将数据发送回Android中的主要活动

Question

我有两个活动:主要活动和儿童活动.
当我按下主活动中的按钮时,将启动子活动.

现在我想将一些数据发送回主屏幕.我使用了Bundle类,但它不起作用.它会抛出一些运行时异常.

这有什么解决方案吗？

Answer 1

根据具体情况,有两种方法可以实现您的目标.

最常见的情况(您的听起来就是这样)是使用子Activity来获取用户输入 - 例如从列表中选择联系人或在对话框中输入数据.在这种情况下,您应该使用startActivityForResult启动您的子Activity.

这提供了一个管道,用于使用数据将数据发送回主Activity setResult.setResult方法接受一个int结果值和一个传递回调用Activity的Intent.

Intent resultIntent = new Intent();
// TODO Add extras or a data URI to this intent as appropriate.
resultIntent.putExtra("some_key", "String data"); 
setResult(Activity.RESULT_OK, resultIntent);
finish();

在调用Activity覆盖中访问返回的数据onActivityResult.requestCode对应于startActivityForResult调用中传入的整数,而resultCode和数据Intent则从子Activity返回.

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
  super.onActivityResult(requestCode, resultCode, data);
  switch(requestCode) {
    case (MY_CHILD_ACTIVITY) : {
      if (resultCode == Activity.RESULT_OK) {
        // TODO Extract the data returned from the child Activity.
        String returnValue = data.getStringExtra("some_key");
      }
      break;
    } 
  }
}

Answer 2

活动1使用startActivityForResult:

startActivityForResult(ActivityTwo, ActivityTwoRequestCode);

活动2已启动,您可以执行操作,关闭活动执行以下操作:

Intent output = new Intent();
output.putExtra(ActivityOne.Number1Code, num1);
output.putExtra(ActivityOne.Number2Code, num2);
setResult(RESULT_OK, output);
finish();

活动1 - 从上一个活动返回将调用onActivityResult:

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == ActivityTwoRequestCode && resultCode == RESULT_OK && data != null) {
        num1 = data.getIntExtra(Number1Code);
        num2 = data.getIntExtra(Number2Code);
    }
}

更新:回答Seenu69的评论,在活动二中,

int result = Integer.parse(EditText1.getText().toString()) 
           + Integer.parse(EditText2.getText().toString());
output.putExtra(ActivityOne.KEY_RESULT, result);

然后在活动一,

int result = data.getExtra(KEY_RESULT);

Answer 3

发回数据

它帮助我在上下文中看到事物.这是一个完整的简单项目,用于发回数据.这是一个图像,而不是提供xml布局文件.

主要活动

• 启动第二个活动startActivityForResult,为其提供任意结果代码.
• 覆盖onActivityResult.当第二个活动完成时调用此方法.您可以通过检查请求代码来确保它实际上是第二个活动.(当您从同一主活动中启动多个不同的活动时,这非常有用.)
• 提取从返回中获得的数据Intent.使用键值对提取数据.

MainActivity.java

public class MainActivity extends AppCompatActivity {

    private static final int SECOND_ACTIVITY_REQUEST_CODE = 0;

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

    // "Go to Second Activity" button click
    public void onButtonClick(View view) {

        // Start the SecondActivity
        Intent intent = new Intent(this, SecondActivity.class);
        startActivityForResult(intent, SECOND_ACTIVITY_REQUEST_CODE);
    }

    // This method is called when the second activity finishes
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        // Check that it is the SecondActivity with an OK result
        if (requestCode == SECOND_ACTIVITY_REQUEST_CODE) {
            if (resultCode == RESULT_OK) {

                // Get String data from Intent
                String returnString = data.getStringExtra("keyName");

                // Set text view with string
                TextView textView = (TextView) findViewById(R.id.textView);
                textView.setText(returnString);
            }
        }
    }
}

第二项活动

• 将要发送回上一个活动的数据放入Intent.数据存储在Intent使用键值对中.
• 将结果设置为RESULT_OK并添加保存数据的意图.
• 致电finish()关闭第二个活动.

SecondActivity.java

public class SecondActivity extends AppCompatActivity {

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

    // "Send text back" button click
    public void onButtonClick(View view) {

        // Get the text from the EditText
        EditText editText = (EditText) findViewById(R.id.editText);
        String stringToPassBack = editText.getText().toString();

        // Put the String to pass back into an Intent and close this activity
        Intent intent = new Intent();
        intent.putExtra("keyName", stringToPassBack);
        setResult(RESULT_OK, intent);
        finish();
    }
}

其他说明

• 如果你是一个片段,它将不知道的含义RESULT_OK.只需使用全名:Activity.RESULT_OK.

也可以看看

• 富勒的答案包括向前传递数据
• 密钥字符串的命名约定

Answer 4

FirstActivity使用startActivityForResult:

Intent intent = new Intent(MainActivity.this,SecondActivity.class);
startActivityForResult(intent, int resultCode); // suppose resultCode == 2

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == 2)
    {
        String message=data.getStringExtra("MESSAGE");
    }
}

在SecondActivity上调用setResult()onClick事件或onBackPressed()

Intent intent=new Intent();
intent.putExtra("MESSAGE",message);
setResult(2,intent);

Answer 5

使用startActivityForResult()方法调用调用子活动Intent

这里有一个例子:http: //developer.android.com/training/notepad/notepad-ex2.html

并在"从屏幕返回结果"中:http: //developer.android.com/guide/faq/commontasks.html#opennewscreen

Answer 6

我已经创建了简单的演示类,以便您更好地参考.

FirstActivity.java

 public class FirstActivity extends AppCompatActivity {

    private static final String TAG = FirstActivity.class.getSimpleName();
    private static final int REQUEST_CODE = 101;
    private Button btnMoveToNextScreen;

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

        btnMoveToNextScreen = (Button) findViewById(R.id.btnMoveToNext);
        btnMoveToNextScreen.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent mIntent = new Intent(FirstActivity.this, SecondActivity.class);
                startActivityForResult(mIntent, REQUEST_CODE);
            }
        });
    }

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

        if(resultCode == RESULT_OK){
            if(requestCode == REQUEST_CODE && data !=null) {
                String strMessage = data.getStringExtra("keyName");
                Log.i(TAG, "onActivityResult: message >>" + strMessage);
            }
        }

    }
}

这是SecondActivity.java

public class SecondActivity extends AppCompatActivity {

    private static final String TAG = SecondActivity.class.getSimpleName();
    private Button btnMoveToPrevious;
    private EditText editText;

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

        editText = (EditText) findViewById(R.id.editText);

        btnMoveToPrevious = (Button) findViewById(R.id.btnMoveToPrevious);
        btnMoveToPrevious.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                String message = editText.getEditableText().toString();

                Intent mIntent = new Intent();
                mIntent.putExtra("keyName", message);
                setResult(RESULT_OK, mIntent);
                finish();

            }
        });

    }
}

Answer 7

2021 年 3 月更新

和Activity v1.2.0和Fragment v1.3.0 一样，新的Activity Result APIs已经被引入。

Activity Result API 提供了用于注册结果、启动结果以及在系统分派结果后处理结果的组件。

所以不再需要使用startActivityForResult和onActivityResult了。

为了使用新 API，您需要在源 Activity 中创建一个 ActivityResultLauncher，指定在目标 Activity 完成并返回所需数据时将运行的回调：

private val intentLauncher =
    registerForActivityResult(ActivityResultContracts.StartActivityForResult()) { result ->

        if (result.resultCode == Activity.RESULT_OK) {
            result.data?.getStringExtra("key1")
            result.data?.getStringExtra("key2")
            result.data?.getStringExtra("key3")
        }
    }

然后，在需要时启动您的意图：

intentLauncher.launch(Intent(this, YourActivity::class.java))

要从目标 Activity 返回数据，您只需添加一个包含要返回到setResult()方法的值的意图：

val data = Intent()
data.putExtra("key1", "value1")
data.putExtra("key2", "value2")
data.putExtra("key3", "value3")

setResult(Activity.RESULT_OK, data)
finish()

有关任何其他信息，请参阅Android 文档

Answer 8

在第一个活动中，您可以使用发送意图 startActivityForResult()，然后在使用结束后从第二个活动中获取结果setResult。

MainActivity.class

public class MainActivity extends AppCompatActivity {

    private static final int SECOND_ACTIVITY_RESULT_CODE = 0;

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

    // "Go to Second Activity" button click
    public void onButtonClick(View view) {

        // Start the SecondActivity
        Intent intent = new Intent(this, SecondActivity.class);
        // send intent for result 
        startActivityForResult(intent, SECOND_ACTIVITY_RESULT_CODE);
    }

    // This method is called when the second activity finishes
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        // check that it is the SecondActivity with an OK result
        if (requestCode == SECOND_ACTIVITY_RESULT_CODE) {
            if (resultCode == RESULT_OK) {

                // get String data from Intent
                String returnString = data.getStringExtra("keyName");

                // set text view with string
                TextView textView = (TextView) findViewById(R.id.textView);
                textView.setText(returnString);
            }
        }
    }
}

SecondActivity.class

public class SecondActivity extends AppCompatActivity {

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

    // "Send text back" button click
    public void onButtonClick(View view) {

        // get the text from the EditText
        EditText editText = (EditText) findViewById(R.id.editText);
        String stringToPassBack = editText.getText().toString();

        // put the String to pass back into an Intent and close this activity
        Intent intent = new Intent();
        intent.putExtra("keyName", stringToPassBack);
        setResult(RESULT_OK, intent);
        finish();
    }
}

Answer 9

所有这些答案都解释了发送数据后需要完成第二个活动的场景。

但如果您不想完成第二个活动并希望将数据发送回第一个活动，那么您可以使用 BroadCastReceiver。

在第二个活动中 -

Intent intent = new Intent("data");
intent.putExtra("some_data", true);
LocalBroadcastManager.getInstance(this).sendBroadcast(intent);

在第一个活动中 -

private BroadcastReceiver tempReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        // do some action
    }
};

在 onCreate() 中注册接收器 -

 LocalBroadcastManager.getInstance(this).registerReceiver(tempReceiver,new IntentFilter("data"));

在 onDestroy() 中取消注册