Activity启动另一个Activity，带结果的返回

朱雀 2022-09-22 11:55 218阅读 0赞

启动其他Activity的一种常用方式就是StartActivity(),但有时候我们期望获取指定Activity返回的结果。这时，就需要使用startActivityForResult()方法，为了获取被启动的 Activity所返回的结果，当前Activity需要重写onActivityResult(int requestCode,int resultCode,Intent intent),其中requestCode代表请求码，resultCode代表返回的结果码，它们都是开发者根据业务自行设定的。这样就可以通过请求码和结果码来判断请求是由谁发出的，结果是由谁返回的。下面通过一个实例来演示：

第一个Activity：

import android.app.Activity;  
    import android.content.Intent;  
    import android.os.Bundle;  
    import android.view.View;  
    import android.view.View.OnClickListener;  
    import android.widget.Button;  
    import android.widget.EditText;  
      
    public class MainActivity extends Activity {  
        Button btn;  
        EditText city;  
      
        @Override  
        protected void onCreate(Bundle savedInstanceState) {  
            super.onCreate(savedInstanceState);  
            setContentView(R.layout.activity_main);  
            city = (EditText) findViewById(R.id.activity_main_et);  
            btn = (Button) findViewById(R.id.activity_main_btn);  
            btn.setOnClickListener(new OnClickListener() {  
      
                @Override  
                public void onClick(View v) {  
                    // 创建需要对应于目标Activity的Intent  
                    Intent intent = new Intent(MainActivity.this,  
                            SelectCityActivity.class);  
                    // 启动指定Activity并等待返回的结果，其中0是请求码，用于标识该请求  
                    startActivityForResult(intent, 0);  
                }  
            });  
        }  
      
        @Override  
        protected void onActivityResult(int requestCode, int resultCode, Intent data) {  
            if (requestCode == 0 && resultCode == 0) {  
                // 取出Intent里的数据  
                String resultCity = data.getStringExtra("city");  
                // 修改city文本框的内容  
                city.setText(resultCity);  
            }  
      
        }  
    }

第二个Activity：

import android.app.ExpandableListActivity;  
    import android.content.Intent;  
    import android.os.Bundle;  
    import android.view.Gravity;  
    import android.view.View;  
    import android.view.ViewGroup;  
    import android.widget.AbsListView;  
    import android.widget.BaseExpandableListAdapter;  
    import android.widget.ExpandableListAdapter;  
    import android.widget.ExpandableListView;  
    import android.widget.ExpandableListView.OnChildClickListener;  
    import android.widget.LinearLayout;  
    import android.widget.TextView;  
      
    public class SelectCityActivity extends ExpandableListActivity {  
        // 定义省份数组  
        private String[] provinces = new String[] { "广东", "广西", "湖南", "四川" };  
        // 定义各省份的城市数组  
        private String[][] cities = new String[][] { { "广州", "深圳", "珠海", "中山" },  
                { "桂林", "柳州", "南宁", "北海" }, { "长沙", "岳阳", "衡阳", "株洲" },  
                { "成都", "绵阳", "广安", "雅安" }, };  
      
        @Override  
        protected void onCreate(Bundle savedInstanceState) {  
            super.onCreate(savedInstanceState);  
            // 创建一个可展开的列表组件ExpandableListAdapter对象  
            ExpandableListAdapter adapter = new BaseExpandableListAdapter() {  
                @Override  
                public boolean isChildSelectable(int groupPosition,  
                        int childPosition) {  
      
                    return true;  
                }  
      
                @Override  
                public boolean hasStableIds() {  
      
                    return true;  
                }  
      
                // 构建每个父列表组件  
                @Override  
                public View getGroupView(int groupPosition, boolean isExpanded,  
                        View convertView, ViewGroup parent) {  
                    // 创建一个LinearLayout对象  
                    LinearLayout ll = new LinearLayout(SelectCityActivity.this);  
                    ll.setOrientation(0);  
                    TextView textView = getTextView();  
                    // 根据groupPosition取provinces对应文本作为textView显示的文本内容  
                    textView.setText(getGroup(groupPosition).toString());  
                    ll.addView(textView);  
                    return ll;  
                }  
      
                @Override  
                public long getGroupId(int groupPosition) {  
                    return groupPosition;  
                }  
      
                @Override  
                public int getGroupCount() {  
      
                    return provinces.length;  
                }  
      
                @Override  
                public Object getGroup(int groupPosition) {  
      
                    return provinces[groupPosition];  
                }  
      
                @Override  
                public int getChildrenCount(int groupPosition) {  
      
                    return cities[groupPosition].length;  
                }  
      
                /** 
                 * 在MainActivity里创建TextView组件 
                 *  
                 * @return TextView 
                 */  
                private TextView getTextView() {  
                    AbsListView.LayoutParams lp = new AbsListView.LayoutParams(  
                            ViewGroup.LayoutParams.MATCH_PARENT, 64);  
                    TextView textView = new TextView(SelectCityActivity.this);  
                    textView.setLayoutParams(lp);  
                    textView.setGravity(Gravity.CENTER_VERTICAL | Gravity.LEFT);  
                    textView.setPadding(36, 0, 0, 0);  
                    textView.setTextSize(20);  
                    return textView;  
                }  
      
                // 构建子列表的数据  
                @Override  
                public View getChildView(int groupPosition, int childPosition,  
                        boolean isLastChild, View convertView, ViewGroup parent) {  
                    TextView textView = getTextView();  
                    // 根据groupPosition和childPosition取cities中对应文本作为textView显示的内容  
                    textView.setText(getChild(groupPosition, childPosition)  
                            .toString());  
                    return textView;  
                }  
      
                @Override  
                public long getChildId(int groupPosition, int childPosition) {  
      
                    return childPosition;  
                }  
      
                @Override  
                public Object getChild(int groupPosition, int childPosition) {  
      
                    return cities[groupPosition][childPosition];  
                }  
            };  
            setListAdapter(adapter);  
            // 为各个子列表绑定事件监听器  
            this.getExpandableListView().setOnChildClickListener(  
                    new OnChildClickListener() {  
      
                        @Override  
                        public boolean onChildClick(ExpandableListView parent,  
                                View v, int groupPosition, int childPosition,  
                                long id) {  
                            Intent intent = getIntent();  
                            Bundle data = new Bundle();  
                            data.putString("city",  
                                    cities[groupPosition][childPosition]);  
                            intent.putExtras(data);  
                            // 设置该SelectCityActivity结果码，并设置结束之后退回的Activity  
                            SelectCityActivity.this.setResult(0, intent);  
                            // 结束SelectCityActivity  
                            SelectCityActivity.this.finish();  
                            return false;  
                        }  
                    });  
        }  
      
    }