Android ContentProvider结合数据库实现菜品的增删改查

布满荆棘的人生 2022-01-30 15:25 255阅读 0赞

ContentProvider提供一个接口，暴露自身的数据，其他应用就可以通过这个接口来实现源数据的增删改查。接下来我们就用一个小案例来演示一下  
因为要用到Android的的四大组件之一ContentProvider，所以这里的数据提供者是menudemo  
链接：[https://pan.baidu.com/s/1i9mdcGIwsDch2MIh-hUTLw][https_pan.baidu.com_s_1i9mdcGIwsDch2MIh-hUTLw]  
提取码：0ytr  
因为上传不了，所以只能给百度云的链接  
下载好了之后，打开新的一个工程，File->New->Import Module，把解压好的menudemo导入  
![在这里插入图片描述][2019051922195268.png]  
运行Menudemo，运行成功的界面的这样的  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyODg5NDc2_size_16_color_FFFFFF_t_70]  
运行的过程中可能会报错，因为这个demo的环境问题跟你电脑上as的版本什么的有冲突，我是把menudemo里的build.gradle改了  
![在这里插入图片描述][2019051922232282.png]  
把这个文件的内容改成如下：

apply plugin: 'com.android.application'
    
    buildscript{
        repositories{
            jcenter()
        }
    
        dependencies{
            classpath "com.android.tools.build:gradle:2.3.3"
        }
    }
    android {
        compileSdkVersion 28
        buildToolsVersion "28.0.3"
    
        defaultConfig {
            applicationId "com.example.menudemo"
            minSdkVersion 15
            targetSdkVersion 28
            versionCode 1
            versionName "1.0"
    
            testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    
        }
        buildTypes {
            release {
                minifyEnabled false
                proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
            }
        }
    }
    
    dependencies {
        implementation fileTree(dir: 'libs', include: ['*.jar'])
        androidTestImplementation('com.android.support.test.espresso:espresso-core:2.2.2', {
            exclude group: 'com.android.support', module: 'support-annotations'
        })
        implementation 'com.android.support:appcompat-v7:24.2.0'
        implementation 'com.android.support.constraint:constraint-layout:2.0.0-beta1'
        testImplementation 'junit:junit:4.12'
    }

具体的话要根据自己电脑的上AS的报错内容来改，不难的  
之后就在新的工程里写代码了  
这个Demo涉及到菜的名字以及类别，所以我们编写两个实体类  
Dishlist.java

package com.example.myapplication.List;
    
    public class DishList {
        public final static String DISH_ID="dish_id";//数据库里面的列名
        public final static String DISH_NAME="dish_name";//数据库里面的列名
        public final static String DISH_TYPE="dish_type";//数据库里面的列名
        private int id;
        private String name;
        private String type;
    
        public DishList() { }
    
        public DishList(int id, String name) {
            this.id = id;
            this.name = name;
        }
    
        public int getId() {
            return id;
        }
    
        public void setId(int id) {
            this.id = id;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public String getType() {
            return type;
        }
    
        public void setType(String type) {
            this.type = type;
        }
    
        @Override
        public String toString() {
            return "DishList{" + "id=" + id + ", name='" + name + '\'' + ", type='" + type + '\'' + '}';
        }
    }

TypeList.java

package com.example.myapplication.List;
    
    import java.util.ArrayList;
    import java.util.List;
    
    public class TypeList {
        public final static String TYPE_ID = "type_id";//数据库里面的列名
        public final static String TYPE_NAME = "type_name";//数据库里面的列名
        private int id;
        private String typename;
        private List<DishList> children = new ArrayList<> ();
        //无参构造
        public TypeList(){}
        //双参构造
        public TypeList(int id, String typename) {
            this.id = id;
            this.typename = typename;
        }
        //添加子item的方法1
        public void addChild(DishList dishList){
            dishList.setType (getTypename ());
            children.add (dishList);
        }
        //添加子item的方法2
        public void addChild(int Childid,String Childname){
            DishList child = new DishList (Childid,Childname);
            child.setType (getTypename ());
            children.add (child);
        }
    
        public int getId() {
            return id;
        }
    
        public void setId(int id) {
            this.id = id;
        }
    
        public String getTypename() {
            return typename;
        }
    
        public void setTypename(String typename) {
            this.typename = typename;
        }
    
        public List<DishList> getChildren() {
            return children;
        }
    
        public void setChildren(List<DishList> children) {
            this.children = children;
        }
    }

然后呢就是编写一下ExpandableListView的布局  
activity\_main.xml

父类的Item，也就是菜品的类型  
activity\_parent\_item.xml

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="56dp"
        android:orientation="horizontal"
        android:gravity="center_vertical">
    
        <TextView
            android:id="@+id/id_parent_item_tv"
            android:layout_width="match_parent"
            android:layout_height="56dp"
            android:layout_marginLeft="40dp"
            android:gravity="center_vertical"
            android:text="xxx"
            android:layout_gravity="center_vertical"
            android:textSize="20dp"
            android:textStyle="bold"/>
    
    </LinearLayout>

子类的Item  
activity\_child\_item.xml

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        xmlns:tools="http://schemas.android.com/tools"
        android:orientation="vertical">
        <TextView
            android:id="@+id/id_child_item_tv"
            android:layout_width="match_parent"
            android:layout_height="40dp"
            android:layout_marginStart="20dp"
            android:gravity="center_vertical"
            android:textSize="16dp"
            android:textStyle="bold"
            tools:text="我是子item" />
    
    </LinearLayout>

然后我们写一个Dao类，获取数据  
loadDataDao

package com.example.myapplication.Dao;
    
    import android.content.ContentResolver;
    import android.database.Cursor;
    import android.net.Uri;
    
    import com.example.myapplication.List.DishList;
    import com.example.myapplication.List.TypeList;
    
    import java.util.ArrayList;
    import java.util.List;
    
    //从Dao这里获取数据
    public class loadDataDao {
        private static final String AUTHORITY = "com.imooc.menuprovider1";
        private static final String TABLE_A = "type_tb";//菜品类型表
        private static final String TABLE_B = "dish_tb";//菜品表
        public static final Uri CONTENT_URI_A = Uri.parse("content://" + AUTHORITY + "/" + TABLE_A);
        public static final Uri CONTENT_URI_B = Uri.parse("content://" + AUTHORITY + "/" + TABLE_B);
        public loadDataDao(){}
        //从ContentProvider中获取数据
        public List<TypeList> loadDatas(ContentResolver resolver){
            //将拿到的数据放回mDatas这里
            List<TypeList> mDatas = new ArrayList<> ();
            //查询菜品类型表
            Cursor c = resolver.query (CONTENT_URI_A,null,null,null,null);
            TypeList parent = null;
            while (c.moveToNext ()) {
                //拿到父类的Item
                parent = new TypeList ();
                int id = c.getInt (c.getColumnIndex (TypeList.TYPE_ID));
                String Typename = c.getString (c.getColumnIndex (TypeList.TYPE_NAME));
                parent.setId (id);
                parent.setTypename (Typename);
                mDatas.add (parent);
            }
            c.close ();
            DishList child = null;
            for (TypeList typeList : mDatas){
                String pTypename = typeList.getTypename ();
                Cursor c1 = resolver.query (CONTENT_URI_B,
                        null,
                        DishList.DISH_TYPE,//指定查询条件为父类的类名,
                        new String[]{pTypename},//指定条件值数组为typename
                        null);
                while (c1.moveToNext ()){
                    child = new DishList ();
                    int cid = c1.getInt (c1.getColumnIndex (DishList.DISH_ID));
                    String cname = c1.getString (c1.getColumnIndex (DishList.DISH_NAME));
                    child.setId (cid);
                    child.setName (cname);
                    child.setType (pTypename);
                    typeList.addChild (child);
                }
                c1.close ();
            }
            return mDatas;
        }
    }

之后写一个适配器将数据显示到ExpandableListView上  
MenuAdapter.java

package com.example.myapplication.Adapter;
    
    import android.app.AlertDialog;
    import android.content.ContentResolver;
    import android.content.Context;
    import android.content.DialogInterface;
    import android.net.Uri;
    import android.util.Log;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.BaseExpandableListAdapter;
    import android.widget.TextView;
    import android.widget.Toast;
    
    import com.example.myapplication.List.DishList;
    import com.example.myapplication.List.TypeList;
    import com.example.myapplication.MainActivity;
    import com.example.myapplication.R;
    import java.util.List;
    
    import static android.provider.ContactsContract.SyncState.CONTENT_URI;
    
    public class MenuAdapter extends BaseExpandableListAdapter {
    
        private static final String AUTHORITY = "com.imooc.menuprovider1";
        private static final String TABLE_A = "type_tb";//菜品类型表
        private static final String TABLE_B = "dish_tb";//菜品表
        public static final Uri CONTENT_URI_A = Uri.parse ("content://" + AUTHORITY + "/" + TABLE_A);
        public static final Uri CONTENT_URI_B = Uri.parse ("content://" + AUTHORITY + "/" + TABLE_B);
        private Context context;
        private List<TypeList> mDatas;//显示的数据集
        private LayoutInflater mInflater;
        private ContentResolver resolver;
    
        public MenuAdapter(Context mContext, List<TypeList> mDatas, CallBack callBack) {
            this.context = mContext;
            this.mInflater = LayoutInflater.from (context);
            this.mDatas = mDatas;
            resolver = context.getContentResolver ();
        }
    
        public interface CallBack {
            void DeleteSuccess(List<TypeList> mDatas);
        }
    
        @Override
        public int getGroupCount() {
            return mDatas.size ();
        }
    
        @Override
        public int getChildrenCount(int groupPosition) {
            return mDatas.get (groupPosition).getChildren ().size ();
        }
    
        @Override
        public Object getGroup(int groupPosition) {
            return mDatas.get (groupPosition);
        }
    
        @Override
        public Object getChild(int groupPosition, int childPosition) {
            return mDatas.get (groupPosition).getChildren ().get (childPosition);
        }
    
        @Override
        public long getGroupId(int groupPosition) {
            return groupPosition;
        }
    
        @Override
        public long getChildId(int groupPosition, int childPosition) {
            return childPosition;
        }
    
        @Override
        public boolean hasStableIds() {
            return true;
        }
    
        @Override
        public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
        //数据缓存
            ParentViewHolder parentViewHolder;
            if (convertView == null) {
                parentViewHolder = new ParentViewHolder ();
                convertView = mInflater.inflate (R.layout.activity_parent_item, parent, false);
                //获取到控件
                parentViewHolder.p_tv = convertView.findViewById (R.id.id_parent_item_tv);
                convertView.setTag (parentViewHolder);
            } else {
                parentViewHolder = (ParentViewHolder) convertView.getTag ();
            }
            parentViewHolder.p_tv.setText (mDatas.get (groupPosition).getTypename ());
            return convertView;
        }
    
        @Override
        public View getChildView(final int groupPosition, final int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
            ChildViewHolder childViewHolder;
            if (convertView == null) {
                childViewHolder = new ChildViewHolder ();
                convertView = mInflater.inflate (R.layout.activity_child_item, parent, false);
                childViewHolder.c_tv = convertView.findViewById (R.id.id_child_item_tv);
                convertView.setTag (childViewHolder);
            } else {
                childViewHolder = (ChildViewHolder) convertView.getTag ();
            }
            childViewHolder.c_tv.setText (mDatas.get (groupPosition).getChildren ().get (childPosition).getName ());
            //子Item的长按事件
            convertView.setOnLongClickListener (new View.OnLongClickListener () {
                @Override
                public boolean onLongClick(View v) {
                    AlertDialog.Builder builder = new AlertDialog.Builder (context);
                    builder.setTitle ("提示！！！");
                    builder.setMessage ("你确定要删除嘛？");
                    builder.setNegativeButton ("取消", new DialogInterface.OnClickListener () {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            dialog.dismiss ();
                        }
                    });
                    builder.setPositiveButton ("确定", new DialogInterface.OnClickListener () {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            resolver.delete (Uri.parse ("content://com.imooc.menuprovider1"), DishList.DISH_ID, new String[]{mDatas.get (groupPosition).getChildren ().
                                    get (childPosition).getId () + ""});
                            mDatas.get (groupPosition).getChildren ().remove (childPosition);
                        }
                    });
                    builder.create ().show ();
                    return true;
                }
            });
            convertView.setOnClickListener (new View.OnClickListener () {
                @Override
                public void onClick(View v) {
                    Log.e ("TAG", "子item的点击事件");
                    Log.e ("TAG", "子item的id是：" + mDatas.get (groupPosition).getChildren ().get (childPosition).getId ());
                }
            });
            return convertView;
        }
    
        @Override
        public boolean isChildSelectable(int groupPosition, int childPosition) {
            return true;
        }
    
        //优化性能
        private static class ParentViewHolder {
            TextView p_tv;
        }
    
        private static class ChildViewHolder {
            TextView c_tv;
        }
    }

之后我们要写一个布局来增加菜品  
activity\_add\_data.xml

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        tools:context=".AddDishAcitivity">
    
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal">
    
            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginLeft="15dp"
                android:layout_marginTop="10dp"
                android:text="类型" />
    
            <Spinner
                android:id="@+id/add_data_sp"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginLeft="15dp"
                android:layout_marginTop="10dp" />
    
        </LinearLayout>
    
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="20dp"
            android:orientation="horizontal">
    
            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginLeft="15dp"
                android:layout_marginTop="10dp"
                android:text="菜名" />
    
            <EditText
                android:id="@+id/add_data_et"
                android:hint="请输入菜名"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginRight="15dp"
                android:layout_marginLeft="15dp"
                android:layout_marginTop="10dp" />
    
        </LinearLayout>
        <Button
            android:id="@+id/add_data_btn"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="确定"/>
    
    </LinearLayout>

编写与之对应的类  
AddDishActivity.java

package com.example.myapplication;
    
    import android.content.ContentResolver;
    import android.content.ContentUris;
    import android.content.ContentValues;
    import android.content.Intent;
    import android.net.Uri;
    import android.os.Bundle;
    import android.support.annotation.Nullable;
    import android.support.v7.app.AppCompatActivity;
    import android.view.View;
    import android.view.WindowManager;
    import android.widget.AdapterView;
    import android.widget.ArrayAdapter;
    import android.widget.Button;
    import android.widget.EditText;
    import android.widget.Spinner;
    import android.widget.Toast;
    
    import com.example.myapplication.List.DishList;
    
    public class AddDishActivity extends AppCompatActivity {
    
        private static final String AUTHORITY = "com.imooc.menuprovider1";
        public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY);
        private Spinner spinner;
        private EditText add_et;
        private Button add_btn;
        private ContentResolver resolver;
        private String dish_type;
        private String dish_name;
    
        @Override
        protected void onCreate(@Nullable Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_add_data);
            //默认键盘不弹出
            getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_HIDDEN);
            initView();
            onListener();
            String[] arr = getResources ().getStringArray (R.array.type_name_string_arr);
            ArrayAdapter<String> mSpinnerAdapter = new ArrayAdapter<String> (AddDishAcitivity.this,
                    android.R.layout.simple_spinner_item,arr);
            spinner.setAdapter (mSpinnerAdapter);
        }
    
        private void onListener() {
            spinner.setOnItemSelectedListener (new AdapterView.OnItemSelectedListener () {
                @Override
                public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                    String[] arr = getResources ().getStringArray (R.array.type_name_string_arr);
                    dish_type = arr[position];
                }
    
                @Override
                public void onNothingSelected(AdapterView<?> parent) {
    
                }
            });
            add_btn.setOnClickListener (new View.OnClickListener () {
                @Override
                public void onClick(View v) {
                    dish_name = add_et.getText ().toString ();
                    ContentValues values = new ContentValues ();
                    values.put(DishList.DISH_NAME, dish_name);
                    values.put(DishList.DISH_TYPE, dish_type);
                    Uri uri = resolver.insert(CONTENT_URI, values);
                    long id = ContentUris.parseId (uri);
                    Toast.makeText (AddDishAcitivity.this,"添加成功"+id,Toast.LENGTH_SHORT).show ();
                    startActivity (new Intent (AddDishAcitivity.this,MainActivity.class));
                    finish ();
                }
            });
        }
    
        private void initView() {
            spinner = findViewById(R.id.add_data_sp);
            add_et = findViewById(R.id.add_data_et);
            add_btn = findViewById(R.id.add_data_btn);
            resolver = getContentResolver();
        }
    }

别忘了要在AndroidMainfest上进行注册  
还有申请对应的权限

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
        <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
        <uses-permission android:name="android.permission.READ_CONTACTS"/>
        <uses-permission android:name="android.permission.WRITE_CONTACTS"/>

最后就是主函数

package com.example.myapplication;
    
    
    import android.Manifest;
    import android.content.ContentResolver;
    import android.content.Intent;
    import android.content.pm.PackageManager;
    import android.support.v4.app.ActivityCompat;
    import android.support.v4.content.ContextCompat;
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.ExpandableListView;
    import android.widget.Spinner;
    import android.widget.TextView;
    
    import com.example.myapplication.Adapter.MenuAdapter;
    import com.example.myapplication.Dao.loadDataDao;
    import com.example.myapplication.List.TypeList;
    
    import java.util.List;
    
    public class MainActivity extends AppCompatActivity {
        private ExpandableListView ex_lv;
        private MenuAdapter mAdapter;
        private List<TypeList> mDatas;
        private TextView addTv;
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate (savedInstanceState);
            setContentView (R.layout.activity_main);
            int permission = ContextCompat.checkSelfPermission (this, Manifest.permission.READ_CONTACTS);
            if(permission != PackageManager.PERMISSION_GRANTED){
                ActivityCompat.requestPermissions (this,new String[]{
                        Manifest.permission.READ_CONTACTS},1);
            }
            int permission1 = ContextCompat.checkSelfPermission (this, Manifest.permission.WRITE_CONTACTS);
            if(permission1 != PackageManager.PERMISSION_GRANTED){
                ActivityCompat.requestPermissions (this,new String[]{
                        Manifest.permission.WRITE_CONTACTS},2);
            }
            ex_lv = findViewById (R.id.id_expandable_lv);
            addTv = findViewById (R.id.add_tv);
            addTv.setOnClickListener (new View.OnClickListener () {
                @Override
                public void onClick(View v) {
                    Intent intent = new Intent (MainActivity.this,AddDishAcitivity.class);
                    startActivity (intent);
                }
            });
            //1.拿到ContentProvider数据
            ContentResolver contentResolver = getContentResolver ();
            mDatas = new loadDataDao ().loadDatas (contentResolver);
            //2.获取适配器对象
            mAdapter = new MenuAdapter (this,mDatas,new MenuAdapter.CallBack (){
                public void DeleteSuccess(List<TypeList> mDatas){
                    mAdapter.notifyDataSetChanged ();
                }
            });
            //将数据显示到ExpandableListView上
            ex_lv.setAdapter (mAdapter);
        }
    }

之后就可以运行在模拟器了  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyODg5NDc2_size_16_color_FFFFFF_t_70 1]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyODg5NDc2_size_16_color_FFFFFF_t_70 2]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyODg5NDc2_size_16_color_FFFFFF_t_70 3]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyODg5NDc2_size_16_color_FFFFFF_t_70 4]  
如果有小伙伴需要这个Demo的话可以留言啦

[https_pan.baidu.com_s_1i9mdcGIwsDch2MIh-hUTLw]: https://pan.baidu.com/s/1i9mdcGIwsDch2MIh-hUTLw
[2019051922195268.png]: /images/20220130/d92510433a794a64bc82d1e5082232dd.png
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[2019051922232282.png]: /images/20220130/c04707a6335d4d42947d2e8ac7dc528a.png
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