android Activity重用機制

原來很懷疑通過startActivityForResult啟動兩個Activity，在onActivityResult中會不會得到不同的結果，經測試，得到的是不同的結果，看來android對Activity的重用做了很多機制，只是我們不知道而已。

OnActivityResult.java ：用來執行兩個startActivityForResult的方法。

public class OnActivityResult extends Activity {    /** Called when the activity is first created. */private Button mActivityButton1;private Button mActivityButton2;private TextView mResultView;public static final int REQUEST_ACTIVITY1 = 1;public static final int REQUEST_ACTIVITY2 = 2;    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);                mActivityButton1 = (Button)findViewById(R.id.startActivity1);        mActivityButton2 = (Button)findViewById(R.id.startActivity2);                mResultView = (TextView)findViewById(R.id.result);                mActivityButton1.setOnClickListener(new ActivityButton1ClickListener());        mActivityButton2.setOnClickListener(new ActivityButton2ClickListener());    }        protected void onActivityResult(int requestCode, int resultCode, Intent data) {    super.onActivityResult(requestCode, resultCode, data);        if(resultCode == RESULT_OK){    switch(requestCode){    case REQUEST_ACTIVITY1:    mResultView.setText("REQUEST_ACTIVITY1");    break;    case REQUEST_ACTIVITY2:    mResultView.setText("REQUEST_ACTIVITY2");    break;    }    }    }        class ActivityButton1ClickListener implements OnClickListener{public void onClick(View v) {// TODO Auto-generated method stubIntent mIntent = new Intent();mIntent.setClass(OnActivityResult.this, PublicActivity.class);try{OnActivityResult.this.startActivityForResult(mIntent, REQUEST_ACTIVITY1);}catch(ActivityNotFoundException e){System.out.println("Exception = " + e.getMessage());}}        }        class ActivityButton2ClickListener implements OnClickListener{public void onClick(View v) {// TODO Auto-generated method stubIntent mIntent = new Intent();mIntent.setClass(OnActivityResult.this, PublicActivity.class);try{OnActivityResult.this.startActivityForResult(mIntent, REQUEST_ACTIVITY2);}catch(ActivityNotFoundException e){System.out.println("Exception = " + e.getMessage());}}    }}

PublicActivity：公用的Activity

public class PublicActivity extends Activity {private Button mBackButton;public void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.public_activity);mBackButton = (Button)findViewById(R.id.back_button);mBackButton.setOnClickListener(new OnBackButtonClickListener());}class OnBackButtonClickListener implements OnClickListener{public void onClick(View v) {// TODO Auto-generated method stubIntent intent = new Intent();Bundle bundle = new Bundle();bundle.putString("result", "PublicActivity");intent.putExtras(bundle);setResult(RESULT_OK, intent);finish();}}}