使用Intent时如何销毁和创建新的活动实例

Question

I have activity flow A->B->C . Now when I click on button in Activity CI want to open activity B by destroying existing instance of Activity B and creating new instance of Activity B. Again if from Activity C if I press on back button then it should open existing instance of Activity B.

Code I tried is :

    Intent i=new Intent(C.this,B.class);
    i.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP|Intent.FLAG_ACTIVITY_NEW_TASK);
    startActivity(i);

So after executing this intent stack should be A->B . But this doesn't creating new instance of Activity B.

Answer 1

What you can do is

1. startActivityForResult() from B activity
2. Then in Acitivity c setResult() OK on button click finish the activity & in onBackpressed() setResult() to fail
3. If you get result OK then finish activity in onActivityResult() in B , If you sent result fail then do nothing in onActivityResult()
4. If you set result OK then start activity b from activity C with fresh instnace

Answer 2

Start Activity C

ActivityB

public class ActivityB extends AppCompatActivity implements View.OnClickListener {

private TextView activity;
private Button start_next_activity;
private final int req_code_reset_activity = 100;

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

    activity.setText("ActivityB");
    start_next_activity.setText("Start Activity C");


    Bundle res = getIntent().getExtras();
    if (res != null) {
        String my_data = res.getString("my_data");
        if (my_data != null)
            activity.setText(activity.getText() + " data rcvd = " + my_data);
    }

}


private void initView() {
    activity = (TextView) findViewById(R.id.activity);
    start_next_activity = (Button) findViewById(R.id.start_next_activity);

    start_next_activity.setOnClickListener(this);
}

@Override
public void onClick(View v) {
    switch (v.getId()) {
        case R.id.start_next_activity:
            startActivityForResult(new Intent(this, ActivityC.class), req_code_reset_activity);
            break;
    }
}

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


    if (requestCode == req_code_reset_activity && resultCode == RESULT_OK) {

        if (null != data) {
            Bundle res = data.getExtras();
            String result = res.getString("my_data");
            Log.d("my_data", "my_data:" + result);
            restartActivity(data);

        }
    }


}

public void restartActivity(Intent intent) {
    Intent mIntent = getIntent();
    mIntent.putExtras(intent.getExtras());
    finish();
    startActivity(mIntent);
}
}

Start Activity C, it will return a result to Activity B weather it needs to re-create or not.

when back button is pressed ActivityB will be restored and when you click on button new instance Activity B will be recreated.

ActivityC

public class ActivityC extends AppCompatActivity implements View.OnClickListener {
private TextView activity;
private Button start_next_activity;
private final int req_code_reset_activity = 100;

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

    activity.setText("ActivityC");
    start_next_activity.setText("New instance Activity B");

}


private void initView() {
    activity = (TextView) findViewById(R.id.activity);
    start_next_activity = (Button) findViewById(R.id.start_next_activity);
    start_next_activity.setOnClickListener(this);
}

@Override
public void onClick(View v) {
    switch (v.getId()) {
        case R.id.start_next_activity:
            Bundle conData = new Bundle();
            conData.putString("my_data", "This is sample data");
            Intent intent = new Intent();
            intent.putExtras(conData);
            setResult(RESULT_OK, intent);
            finish();
            break;
    }
}
}