网络通信——下载管理器DownloadManager——主动轮询当前的下载进度

女爷i 2024-04-01 08:22 64阅读 0赞

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<?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        package="com.example.myapplication">
    
        
        <uses-permission android:name="android.permission.INTERNET" />
        
        <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
        <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
        
        <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
        <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
        
        <uses-permission android:name="android.permission.DOWNLOAD_WITHOUT_NOTIFICATION" />
    
    
        
        <uses-permission android:name="android.permission.DOWNLOAD_WITHOUT_NOTIFICATION" />
    
        
        <uses-permission android:name="android.permission.CAMERA" />
        
        <uses-permission android:name="android.permission.RECORD_AUDIO" />
        
        <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
        <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
        <uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />
    
        <application
            android:allowBackup="true"
            android:dataExtractionRules="@xml/data_extraction_rules"
            android:fullBackupContent="@xml/backup_rules"
            android:icon="@mipmap/ic_launcher"
            android:label="@string/app_name"
            android:roundIcon="@mipmap/ic_launcher_round"
            android:supportsRtl="true"
            android:theme="@style/Theme.MyApplication"
            android:usesCleartextTraffic="true"
            tools:targetApi="31">
            <activity
                android:name=".MainActivity7"
                android:exported="false" />
            <activity
                android:name=".MainActivity6"
                android:exported="false" />
            <activity
                android:name=".MainActivity5"
                android:exported="false"
                android:label="@string/title_activity_main5" />
            <activity
                android:name=".MainActivity4"
                android:exported="false"
                android:label="@string/title_activity_main4" />
            <activity
                android:name=".MainActivity3"
                android:exported="false"
                android:label="@string/title_activity_main3" />
            <activity
                android:name=".MainActivity2"
                android:exported="false"
                android:label="@string/title_activity_main2" />
            <activity
                android:name=".MainActivity"
                android:exported="true">
    
                
                <intent-filter>
                    <action android:name="android.intent.action.MAIN" />
    
                    <category android:name="android.intent.category.LAUNCHER" />
                </intent-filter>
            </activity>
        </application>
    
    </manifest>

布局：

![e6c56a6b50ebd9150a7129b8adf8f48a.png][]

TextProgressCircle

package com.example.myapplication.widget;
    
    import android.annotation.SuppressLint;
    import android.content.Context;
    import android.graphics.Canvas;
    import android.graphics.Color;
    import android.graphics.Paint;
    import android.graphics.Paint.Style;
    import android.graphics.Rect;
    import android.graphics.RectF;
    import android.util.AttributeSet;
    import android.view.View;
    
    import com.example.myapplication.util.Utils;
    
    @SuppressLint("DrawAllocation")
    public class TextProgressCircle extends View {
        private Context mContext; // 声明一个上下文对象
        private Paint mPaintBack = new Paint(); // 声明一个背景画笔对象
        private Paint mPaintFore = new Paint(); // 声明一个前景画笔对象
        private Paint mPaintText = new Paint(); // 声明一个文本画笔对象
        private int mLineWidth; // 线条的宽度
        private int mProgress = 0; // 进度值
    
        public TextProgressCircle(Context context) {
            this(context, null);
        }
    
        public TextProgressCircle(Context context, AttributeSet attr) {
            super(context, attr);
            mContext = context;
            initPaint(); // 初始化画笔
        }
    
        // 初始化画笔
        private void initPaint() {
            mLineWidth = Utils.dip2px(mContext, 10);
            // 以下初始化背景画笔
            mPaintBack.setColor(Color.LTGRAY);
            mPaintBack.setStrokeWidth(mLineWidth);
            mPaintBack.setStyle(Style.STROKE);
            // 以下初始化前景画笔
            mPaintFore.setColor(Color.GREEN);
            mPaintFore.setStrokeWidth(mLineWidth);
            mPaintFore.setStyle(Style.STROKE);
            // 以下初始化文本画笔
            mPaintText.setColor(Color.BLUE);
            mPaintText.setTextSize(Utils.dip2px(mContext, 50));
        }
    
        @Override
        protected void onDraw(Canvas canvas) {
            super.onDraw(canvas);
            int width = getMeasuredWidth(); // 获得视图测量后的宽度
            int height = getMeasuredHeight(); // 获得视图测量后的高度
            int diameter = Math.min(width, height); // 宽度和高度取较小的那个作为进度圆圈的直径
            RectF rectF = new RectF((width - diameter) / 2 + mLineWidth, (height - diameter) / 2 + mLineWidth,
                    (width + diameter) / 2 - mLineWidth, (height + diameter) / 2 - mLineWidth);
            // 在画布上绘制完整的背景圆圈
            canvas.drawArc(rectF, 0, 360, false, mPaintBack);
            // 在画布上绘制规定进度的前景圆弧
            canvas.drawArc(rectF, 0, mProgress * 360 / 100, false, mPaintFore);
            String text = mProgress + "%";
            Rect rect = new Rect();
            mPaintText.getTextBounds(text, 0, text.length(), rect); // 获得进度文字的矩形边界
            int x = (width / 2) - rect.centerX(); // 计算进度文字左上角的横坐标
            int y = (height / 2) - rect.centerY(); // 计算进度文字左上角的纵坐标
            canvas.drawText(text, x, y, mPaintText); // 在画布上绘制进度文字
        }
    
        // 设置进度值
        public void setProgress(int progress) {
            mProgress = progress;
            invalidate(); // 立刻刷新视图
        }
    
    }

MainActivity

package com.example.myapplication;
    
    import android.annotation.SuppressLint;
    import android.app.DownloadManager;
    import android.app.DownloadManager.Request;
    import android.content.Context;
    import android.database.Cursor;
    import android.net.Uri;
    import android.os.Bundle;
    import android.os.Environment;
    import android.os.Handler;
    import android.os.Looper;
    import android.view.View;
    import android.widget.AdapterView;
    import android.widget.AdapterView.OnItemSelectedListener;
    import android.widget.ArrayAdapter;
    import android.widget.ImageView;
    import android.widget.Spinner;
    import android.widget.TextView;
    
    import androidx.appcompat.app.AppCompatActivity;
    
    import com.example.myapplication.widget.TextProgressCircle;
    
    import java.util.HashMap;
    
    @SuppressLint({
         "SetTextI18n","DefaultLocale"})
    public class MainActivity extends AppCompatActivity
    {
    
        private Spinner sp_image_url; // 图片链接的下拉框
        private ImageView iv_image_url;
        private TextProgressCircle tpc_progress; // 定义一个文本进度圈对象
        private TextView tv_image_result;
        private boolean isFirstSelect = true; // 是否首次选择
        private Uri mImageUri; // 图片的路径对象
        private DownloadManager mDownloadManager; // 声明一个下载管理器对象
        private long mDownloadId = 0; // 当前任务的下载编号
        private static HashMap<Integer, String> mStatusMap = new HashMap<Integer, String>(); // 下载状态映射
        static { // 初始化下载状态映射
            mStatusMap.put(DownloadManager.STATUS_PENDING, "挂起");
            mStatusMap.put(DownloadManager.STATUS_RUNNING, "运行中");
            mStatusMap.put(DownloadManager.STATUS_PAUSED, "暂停");
            mStatusMap.put(DownloadManager.STATUS_SUCCESSFUL, "成功");
            mStatusMap.put(DownloadManager.STATUS_FAILED, "失败");
        }
        private String[] imageDescArray = {
                "洱海公园", "丹凤亭", "宛在堂", "满庭芳", "玉带桥", "眺望洱海", "洱海女儿", "海心亭", "洱海岸边", "烟波浩渺"
        };
        private String[] imageUrlArray = {
                "https://b255.photo.store.qq.com/psb?/V11ZojBI0Zz6pV/nYJcslMIrGeDrujE5KZF2xBW8rjXMIVetZfrOAlSamM!/b/dPwxB5iaEQAA",
                "https://b255.photo.store.qq.com/psb?/V11ZojBI0Zz6pV/Adcl9XVS.RBED4D8shjceYHOhhR*6mcNyCcq24kJG2k!/b/dPwxB5iYEQAA",
                "https://b255.photo.store.qq.com/psb?/V11ZojBI0Zz6pV/bg*X6nT03YUReoJ97ked266WlWG3IzLjBdwHpKqkhYY!/b/dOg5CpjZEAAA",
                "https://b255.photo.store.qq.com/psb?/V11ZojBI0Zz6pV/JOPAKl9BO1wragCEIVzXLlHwj83qVhb8uNuHdmVRwP4!/b/dPwxB5iSEQAA",
                "https://b255.photo.store.qq.com/psb?/V11ZojBI0Zz6pV/7hHOgBEOBshH*7YAUx7RP0JzPuxRBD727mblw9TObhc!/b/dG4WB5i2EgAA",
                "https://b255.photo.store.qq.com/psb?/V11ZojBI0Zz6pV/m4Rjx20D9iFL0D5emuYqMMDji*HGQ2w2BWqv0zK*tRk!/b/dGp**5dYEAAA",
                "https://b255.photo.store.qq.com/psb?/V11ZojBI0Zz6pV/swfCMVl7Oefv8xgboV3OqkrahEs33KO7XwwH6hh7bnY!/b/dECE*5e9EgAA",
                "https://b256.photo.store.qq.com/psb?/V11ZojBI0Zz6pV/tpRlB0oozaD9PyBtCmf3pQ5QY0keJJxYGX93I7n5NwQ!/b/dAyVmZiVEQAA",
                "https://b256.photo.store.qq.com/psb?/V11ZojBI0Zz6pV/wMX2*LM6y.mBsFIYu8spAa7xXWUkPD.GHyazd.vMmYA!/b/dGYwoZjREQAA",
                "https://b255.photo.store.qq.com/psb?/V11ZojBI0Zz6pV/2vl1n0KmKTPCv944MVJgLxKAhMiM*sqajIFQ43c*9DM!/b/dPaoCJhuEQAA",
        };
    
        @Override
        protected void onCreate(Bundle savedInstanceState)
        {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            iv_image_url = findViewById(R.id.iv_image_url);
            // 从布局文件中获取名叫tpc_progress的文本进度圈
            tpc_progress = findViewById(R.id.tpc_progress);
            tv_image_result = findViewById(R.id.tv_image_result);
            // 从系统服务中获取下载管理器
            mDownloadManager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
            initImageSpinner(); // 初始化下载图片的下拉框
        }
    
        // 初始化下载图片的下拉框
        private void initImageSpinner() {
            ArrayAdapter<String> imageUrlAdapter = new ArrayAdapter<String>(this,
                    R.layout.item_select, imageDescArray);
            sp_image_url = findViewById(R.id.sp_image_url);
            sp_image_url.setPrompt("请选择要下载的图片");
            sp_image_url.setAdapter(imageUrlAdapter);
            sp_image_url.setOnItemSelectedListener(new ImageUrlSelectedListener());
            sp_image_url.setSelection(0);
        }
    
        class ImageUrlSelectedListener implements OnItemSelectedListener {
            public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
                if (isFirstSelect) { // 刚打开页面时不需要执行下载动作
                    isFirstSelect = false;
                    return;
                }
                startDownload(arg2); // 开始下载指定序号的图片文件
            }
    
            public void onNothingSelected(AdapterView<?> arg0) {}
        }
    
        // 开始下载指定序号的图片文件
        private void startDownload(int pos) {
            iv_image_url.setImageDrawable(null); // 清空图像视图
            tpc_progress.setProgress(0); // 设置文本进度圈的当前进度为0，最大进度为100
            tpc_progress.setVisibility(View.VISIBLE); // 显示文本进度圈
            Uri uri = Uri.parse(imageUrlArray[pos]); // 根据图片的下载地址构建一个路径对象
            Request down = new Request(uri); // 创建一个下载请求对象，指定从哪里下载文件
            // 设置允许下载的网络类型
            down.setAllowedNetworkTypes(Request.NETWORK_MOBILE | Request.NETWORK_WIFI);
            down.setNotificationVisibility(Request.VISIBILITY_HIDDEN); // 设置不在通知栏显示
            // 设置下载文件在本地的保存路径
            down.setDestinationInExternalFilesDir(this, Environment.DIRECTORY_DCIM, pos + ".jpg");
            mDownloadId = mDownloadManager.enqueue(down); // 把下载请求对象加入到下载队列
            mHandler.post(mRefresh); // 启动下载进度的刷新任务
        }
    
        private Handler mHandler = new Handler(Looper.myLooper()); // 声明一个处理器对象
        // 定义一个下载进度的刷新任务
        private Runnable mRefresh = new Runnable() {
            @Override
            public void run() {
                boolean isFinish = false;
                DownloadManager.Query down_query = new DownloadManager.Query(); // 创建一个下载查询对象，按照下载编号过滤
                down_query.setFilterById(mDownloadId); // 设置下载查询对象的编号过滤器
                // 向下载管理器查询下载任务，并返回查询结果集的游标
                Cursor cursor = mDownloadManager.query(down_query);
                while (cursor.moveToNext()) {
                    int uriIdx = cursor.getColumnIndex(DownloadManager.COLUMN_LOCAL_URI);
                    int mediaIdx = cursor.getColumnIndex(DownloadManager.COLUMN_MEDIA_TYPE);
                    int totalIdx = cursor.getColumnIndex(DownloadManager.COLUMN_TOTAL_SIZE_BYTES);
                    int nowIdx = cursor.getColumnIndex(DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR);
                    int statusIdx = cursor.getColumnIndex(DownloadManager.COLUMN_STATUS);
                    if (cursor.getString(uriIdx) == null) {
                        break;
                    }
                    // 根据总大小和已下载大小，计算当前的下载进度
                    int progress = (int) (100 * cursor.getLong(nowIdx) / cursor.getLong(totalIdx));
                    tpc_progress.setProgress(progress); // 设置文本进度圈的当前进度
                    if (progress == 100) { // 下载完毕
                        isFinish = true;
                    }
                    // 获得实际的下载状态
                    int status = isFinish ? DownloadManager.STATUS_SUCCESSFUL : cursor.getInt(statusIdx);
                    mImageUri = Uri.parse(cursor.getString(uriIdx));
                    String desc = String.format("文件路径：%s\n媒体类型：%s\n文件总大小：%d字节" +
                                    "\n已下载大小：%d字节\n下载进度：%d%%\n下载状态：%s",
                            mImageUri.toString(), cursor.getString(mediaIdx), cursor.getLong(totalIdx),
                            cursor.getLong(nowIdx), progress, mStatusMap.get(status));
                    tv_image_result.setText(desc); // 显示图片下载任务的下载详情
                }
                cursor.close(); // 关闭数据库游标
                if (!isFinish) { // 下载未完成，则继续刷新
                    mHandler.postDelayed(this, 50); // 延迟50毫秒后再次启动刷新任务
                } else { // 下载已完成，则显示图片
                    tpc_progress.setVisibility(View.INVISIBLE); // 隐藏文本进度圈
                    iv_image_url.setImageURI(mImageUri); // 设置图像视图的图片路径
                }
            }
        };
    
        @Override
        protected void onDestroy() {
            super.onDestroy();
            mHandler.removeCallbacks(mRefresh); // 移除刷新任务
        }
    }

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