Android中启动其他Activity并返回结果

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：

package com.lovo.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;@Overrideprotected 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() {@Overridepublic void onClick(View v) {// 创建需要对应于目标Activity的IntentIntent 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);}});}@Overrideprotected 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：

package com.lovo.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" }, };@Overrideprotected 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() {@Overridepublic boolean isChildSelectable(int groupPosition,int childPosition) {return true;}@Overridepublic boolean hasStableIds() {return true;}// 构建每个父列表组件@Overridepublic 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;}@Overridepublic long getGroupId(int groupPosition) {return groupPosition;}@Overridepublic int getGroupCount() {return provinces.length;}@Overridepublic Object getGroup(int groupPosition) {return provinces[groupPosition];}@Overridepublic 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@Overridepublic 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;}@Overridepublic long getChildId(int groupPosition, int childPosition) {return childPosition;}@Overridepublic 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() {@Overridepublic 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ActivitySelectCityActivity.this.setResult(0, intent);// 结束SelectCityActivitySelectCityActivity.this.finish();return false;}});}}

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