Android中啟動其他Activity并返回結果
啟動其他Activity的一種常用方式就是StartActivity(),但有時候我們期望獲取指定Activity返回的結果。這時，就需要使用startActivityForResult()方法，為了獲取被啟動的 Activity所返回的結果，當前Activity需要重寫onActivityResult(int requestCode,int resultCode,Intent intent),其中requestCode代表請求碼，resultCode代表返回的結果碼，它們都是開發者根據業務自行設定的。這樣就可以通過請求碼和結果碼來判斷請求是由誰發出的，結果是由誰返回的。下面通過一個實例來演示：
第一個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) {
// 創建需要對應于目標Activity的Intent
Intent intent = new Intent(MainActivity.this,
SelectCityActivity.class);
// 啟動指定Activity并等待返回的結果，其中0是請求碼，用于標識該請求
startActivityForResult(intent, 0);
}
});
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == 0 && resultCode == 0) {
// 取出Intent里的數據
String resultCity = data.getStringExtra("city");
// 修改city文本框的內容
city.setText(resultCity);
}
}
}
第二個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 {
// 定義省份數組
private String[] provinces = new String[] { "廣東", "廣西", "湖南", "四川" };
// 定義各省份的城市數組
private String[][] cities = new String[][] { { "廣州", "深圳", "珠海", "中山" },
{ "桂林", "柳州", "南寧", "北海" }, { "長沙", "岳陽", "衡陽", "株洲" },
{ "成都", "綿陽", "廣安", "雅安" }, };
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// 創建一個可展開的列表組件ExpandableListAdapter對象
ExpandableListAdapter adapter = new BaseExpandableListAdapter() {
@Override
public boolean isChildSelectable(int groupPosition,
int childPosition) {
return true;
}
@Override
public boolean hasStableIds() {
return true;
}
// 構建每個父列表組件
@Override
public View getGroupView(int groupPosition, boolean isExpanded,
View convertView, ViewGroup parent) {
// 創建一個LinearLayout對象
LinearLayout ll = new LinearLayout(SelectCityActivity.this);
ll.setOrientation(0);
TextView textView = getTextView();
// 根據groupPosition取provinces對應文本作為textView顯示的文本內容
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里創建TextView組件
*
* @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;
}
// 構建子列表的數據
@Override
public View getChildView(int groupPosition, int childPosition,
boolean isLastChild, View convertView, ViewGroup parent) {
TextView textView = getTextView();
// 根據groupPosition和childPosition取cities中對應文本作為textView顯示的內容
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);
// 為各個子列表綁定事件監聽器
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);
// 設置該SelectCityActivity結果碼，并設置結束之后退回的Activity
SelectCityActivity.this.setResult(0, intent);
// 結束SelectCityActivity
SelectCityActivity.this.finish();
return false;
}
});
}
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