Question

我有一项活动和第二项活动。在第二个活动中，我需要关闭活动，然后再次在第一个活动中向用户显示警报。

以下是我用于调出警报并关闭活动的当前代码：

String message = "message";

AlertDialog alertDialog = new AlertDialog.Builder(SecondActivity.this).create();
alertDialog.setMessage(message);
alertDialog.show();

alertDialog.setOnDismissListener(new OnDismissListener() 
{
    public void onDismiss(final DialogInterface dialog) 
    {
        finish();
    }
});

那么我怎样才能使第二个活动finishes，然后一旦回到第一个活动，就会向用户显示警告？

我也尝试了这个：

String message = "message";

finish();

AlertDialog alertDialog = new AlertDialog.Builder(FirstActivity.class).create();
alertDialog.setMessage(message);
alertDialog.show();

但是我收到了这个错误：

The constructor AlertDialog.Builder(Class<FirstActivity>) is undefined

Answer 1

您需要使用startActivityForResult()方法启动第二项活动。然后，关闭第二个活动后，将调用第一个活动的onActivityResult()方法。在那里你可以打开一个对话框。这是代码示例。

class SecondActivity extends Actvitiy {

    // for instance you close your activity here
    public void onClick(View view) {
        // you have an int to get back
        int resultValue = ...;

        // store your variables into resulting intent
        Intent data = new Intent();
        data.putExtra(FirstActivity.EXT_RESULT, resultValue);

        // store result with data
        setResult(RESULT_OK, data);

        // finish activity
        finish();
    }
}

class FirstActivity extends Activity {

    public static final String EXT_RESULT = "result-value";
    public static final int REQ_SECOND_ACTIVITY = 100;

    // call this method to launch second activity
    private void launchSecondActicity() {
        startActivityForResult(
            new Intent(this, SecondActivity.class), REQ_SECOND_ACTIVITY);
    }

    @Override
    public onActivityResult(int requestCode, int resultCode, Intent data) {
        // this gets called when second activity is closed
        if (resultCode == RESULT_OK && requestCode == REQ_SECOND_ACTIVITY) {

            // read your value
            int resultValue = data.getIntExtra(EXT_RESULT, 0);

            // open your dialog here
            ...
        }
    }
}

Answer 2

我需要使用startActivityForResult方法从第一个活动开始第二个活动，然后将result从first activity传递到second activity。

第二项活动：

Intent data = new Intent(); 
data.putExtra("reference for the message", message); // give the intent the String value to be passed to other activity
setResult(Activity.RESULT_OK, data);

finish();

第一项活动：

将其放在first activity class：

的顶部

public static final int REQ_SECOND_ACTIVITY = 100;

这是从second activity：

开始first activity的方法

startActivityForResult(new Intent(FirstActivity.this, SecondActivity.class), REQ_SECOND_ACTIVITY);

最后，将此方法添加到first activity class：

// this method gets called when the second activity is closed
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    if (resultCode == RESULT_OK && requestCode == REQ_SECOND_ACTIVITY) 
    {   
        String message = data.getStringExtra("reference for the message");

        AlertDialog alertDialog = new AlertDialog.Builder(FirstActivity.this).create();
        alertDialog.setMessage(message);
        alertDialog.show();        
    }
}

此方法由用户beworker和letroll上的question组合而成。

如何向其他活动显示警报

2 个答案:

第二项活动：

第一项活动：