用 startActivityForResult 方法启动 Activity 的简单使用

Activity 启动 Activity 的方法有两种：

1. startActivity(Intent intent)；

2. startActivityForResult(Intent intent, int requestCode);

第二个启动方法以指定的请求码（requestCode）启动 Activity，请求码由用户自己设置，用于标识请求来源；在以第2中方法中启动的 Activity 中以 finishActivity(intrequestCode) 方法来结束。

要获取被启动的 Activity 所返回的结果：

1.当前 Activity 需要重写 onActivityResult(int requestCode, int resultCode, Intent intent)；resultCode 代表 Activity 所返回的结果码，该结果码由用户设置；

2.需要在被启动的 Activity 中调用 setResult() 方法来处理结果。

下面是一个以startActivityForResult(Intent intent, int requestCode)方法启动的 Activity 的示例，效果如下：



layout_main.xml 布局文件：

<RelativeLayout 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:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context=".MainActivity">

<Button
android:id="@+id/bt"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/text1"/>

<EditText
android:id="@+id/edit1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/bt"/>

</RelativeLayout>

MainActivity.java 代码：

package com.android.scxh.activityforresult;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

public class MainActivity extends Activity {

Button bn;
EditText city;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

bn = (Button)findViewById(R.id.bt);
city = (EditText)findViewById(R.id.edit1);

bn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {

Intent intent = new Intent(MainActivity.this, SelectCityActivity.class);
// 请求码为 0
startActivityForResult(intent, 0);
}
});
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {

// 只有当 requestCode 和 resultCode 同时为 0 时，才处理结果
if (requestCode == 0 && resultCode == 0) {
Bundle data1 = data.getExtras();

String resultCity = data1.getString("city");

city.setText(resultCity);

}
}
}

被启动的 SelectCityActivity.java 代码：

package com.android.scxh.activityforresult;

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.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;

public class SelectCityActivity extends ExpandableListActivity{

private String[] provinces = new String[]{"广东", "四川", "河南"};

private String[][] cities = new String[][]{
{"广州", "深圳", "东莞", "中山"},
{"成都", "绵阳", "乐山", "德阳"},
{"洛阳", "开封", "郑州", "许昌"}
};

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

ExpandableListAdapter adapter = new BaseExpandableListAdapter() {
@Override
public int getGroupCount() {
return provinces.length;
}

@Override
public int getChildrenCount(int groupPosition) {
return cities[groupPosition].length;
}

// 获取指定组位置处的组的数据
@Override
public Object getGroup(int groupPosition) {
return provinces[groupPosition];
}

// 获取指定组 位置，指定子列表处的子列表项数据
@Override
public Object getChild(int groupPosition, int childPosition) {
return cities[groupPosition][childPosition];
}

@Override
public long getGroupId(int groupPosition) {
return groupPosition;
}

@Override
public long getChildId(int groupPosition, int childPosition) {
return childPosition;
}

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;
}

@Override
public boolean hasStableIds() {
return true;
}

// 决定每个组选项的外观
@Override
public View getGroupView(int groupPosition, boolean isExpanded,
View convertView, ViewGroup parent) {

LinearLayout ll = new LinearLayout(SelectCityActivity.this);
ll.setOrientation(LinearLayout.HORIZONTAL);

ImageView logo = new ImageView(SelectCityActivity.this);
ll.addView(logo);

TextView textView = getTextView();
textView.setText(getGroup(groupPosition).toString());
ll.addView(textView);

return ll;
}

// 决定每个子选项的外观
@Override
public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {

TextView textView = getTextView();
textView.setText(getChild(groupPosition, childPosition).toString());

return textView;
}

@Override
public boolean isChildSelectable(int groupPosition, int childPosition) {
return true;
}
};

setListAdapter(adapter);

getExpandableListView().setOnChildClickListener(
new ExpandableListView.OnChildClickListener() {
@Override
public boolean onChildClick(ExpandableListView parent, View v,
int groupPosition, int childPosition, long id) {

// 获取 MainActivity 对应的 Intent
Intent intent = getIntent();
intent.putExtra("city", cities[groupPosition][childPosition]);
// 设置该 SelectCityActivity 的结束码，设置结束之后返回 MainActivity
SelectCityActivity.this.setResult(0, intent);
// 结束 SelectCityActivity
SelectCityActivity.this.finish();

return false;
}
});
}
}

此外还需要在 AndroidManifest.xml 文件中为 SelectCityActivity 注册：

<activity android:name=".SelectCityActivity"/>