[android]startActivityForResult方法簡介

Activity1跳轉到Activity2，用startActivity()；如果由Activity1跳轉到Activity2，需要再由Activity2回到Activity1呢？

可能有人說：那我在Activity2中再次使用startActivity()不就可以了，是的，但是startActivityForResult()能夠直接完成這項工作

Activity startActivityForResult(Intent intent,int requestCode)步驟：---requestCode--0--用此來做個標記，要求大於等於0

1）在源Activity中使用startActivityForResult()方法啓動目標Activity

2）在目標Activity中使用setResult()方法設置返回值，並調用finish()方法結束目標Activity

3）在源Activity中重寫onActivityResult()方法，獲得從目標Activity中返回的值

源Activity代碼：

public class MainActivity extends Activity {
	private Button button;

	private void setupView() {
		button = (Button) findViewById(R.id.button);
		button.setText("啓動TargetActivity");
	}
	
	public void doClick(View v){
		//啓動目標Activity
		Intent intent = new Intent(this,TargetActivity.class);
		intent.putExtra("name", "zhangsan");
//		startActivity(intent);
		startActivityForResult(intent, 0);
	}

	/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		setupView();
	}
	
	@Override
	protected void onActivityResult(int requestCode, int resultCode, Intent data) {
		// TODO Auto-generated method stub
//		super.onActivityResult(requestCode, resultCode, data);
		switch (resultCode) {
		case RESULT_CANCELED:
			Toast.makeText(this, "未正確返回結果.", Toast.LENGTH_LONG).show();
			break;

		case RESULT_OK:
			int age = data.getIntExtra("age", -1);
			if(age!=-1){
				Toast.makeText(this, "返回的年齡是：" + age, Toast.LENGTH_LONG).show();
			}
			break;
		}
	}
}

目標Activity代碼：

public class TargetActivity extends Activity {
	private Button button;
	private String name;
	private void setupView(){
		button = (Button)findViewById(R.id.button);
		button.setText("返回");
	}
	
	public void doClick(View v){
		//判斷姓名，根據姓名獲取對應的年齡
		int age = -1;
		if("zhangsan".equals(name)){
			age = 19;
		}else if("lisi".equals(name)){
			age = 20;
		}else if("wangwu".equals(name)){
			age = 30;
		}else{
			age = 18;
		}
		
		//創建intent對象，設置年齡爲附加參數
		Intent intent = new Intent();
		intent.putExtra("age", age);
		
		//設置返回值，將intent對象作爲數據返回到源Activity
		setResult(RESULT_OK, intent);
		finish();
	}
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		setupView();//初始化界面
		
		//獲取源Activity傳遞過來的姓名信息
		name = getIntent().getStringExtra("name");
		//如果未正確獲得姓名，則返回RESULT_CALCELED
		if(name==null){
			setResult(RESULT_CANCELED);
			finish();
		}
	}
}