在我的活动中，我通过startActivityForResult从主活动中调用第二个活动。在我的第二个活动中，有一些方法完成这个活动(可能没有结果)，但是，只有其中一个返回结果。
例如，从主活动中调用第二个活动。在这个活动中，我正在检查手机的一些功能，比如它是否有摄像头。如果没有，我就关闭这个活动。此外，在MediaRecorder或MediaPlayer的准备过程中，如果发生问题，我将关闭此活动。
如果它的设备有摄像头，并且录制完成，那么在录制视频后，如果用户单击done按钮，那么我将把结果(录制视频的地址)发送回主活动。
如何检查主活动的结果?
当前回答
你需要重写Activity.onActivityResult():
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode == RESULT_CODE_ONE) {
String a = data.getStringExtra("RESULT_CODE_ONE");
}
else if(resultCode == RESULT_CODE_TWO){
// b was clicked
}
else{
}
}
其他回答
如何检查主要活动的结果?
你需要重写Activity.onActivityResult()，然后检查它的参数:
requestCode标识哪个应用程序返回了这些结果。这是在调用startActivityForResult()时由您定义的。 resultCode告诉你这个应用程序是成功了、失败了还是其他什么 data保存此应用程序返回的任何信息。这可能是空的。
从你的FirstActivity，使用startActivityForResult()方法调用SecondActivity。
例如:
int LAUNCH_SECOND_ACTIVITY = 1
Intent i = new Intent(this, SecondActivity.class);
startActivityForResult(i, LAUNCH_SECOND_ACTIVITY);
在你的SecondActivity中，设置你想返回给FirstActivity的数据。如果你不想返回，就不要设置任何。
例如:在SecondActivity中，如果你想发回数据:
Intent returnIntent = new Intent();
returnIntent.putExtra("result",result);
setResult(Activity.RESULT_OK,returnIntent);
finish();
如果你不想返回数据:
Intent returnIntent = new Intent();
setResult(Activity.RESULT_CANCELED, returnIntent);
finish();
现在在FirstActivity类中，为onActivityResult()方法编写以下代码。
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == LAUNCH_SECOND_ACTIVITY) {
if(resultCode == Activity.RESULT_OK){
String result=data.getStringExtra("result");
}
if (resultCode == Activity.RESULT_CANCELED) {
// Write your code if there's no result
}
}
} //onActivityResult
要在Kotlin中以更好的方式实现两个活动之间的数据传递，请参见“在活动之间传递数据的更好方式”。
你的主要活动
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
findViewById(R.id.takeCam).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent=new Intent(getApplicationContext(),TakePhotoActivity.class);
intent.putExtra("Mode","Take");
startActivity(intent);
}
});
findViewById(R.id.selectGal).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent=new Intent(getApplicationContext(),TakePhotoActivity.class);
intent.putExtra("Mode","Gallery");
startActivity(intent);
}
});
}
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
}
在第二个活动中显示
private static final int CAMERA_REQUEST = 1888;
private ImageView imageView;
private static final int MY_CAMERA_PERMISSION_CODE = 100;
private static final int PICK_PHOTO_FOR_AVATAR = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_take_photo);
imageView=findViewById(R.id.imageView);
if(getIntent().getStringExtra("Mode").equals("Gallery"))
{
pickImage();
}
else {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (checkSelfPermission(Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
requestPermissions(new String[]{Manifest.permission.CAMERA}, MY_CAMERA_PERMISSION_CODE);
} else {
Intent cameraIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
startActivityForResult(cameraIntent, CAMERA_REQUEST);
}
}
}
}
public void pickImage() {
Intent intent = new Intent(Intent.ACTION_PICK);
intent.setType("image/*");
startActivityForResult(intent, PICK_PHOTO_FOR_AVATAR);
}
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults)
{
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
if (requestCode == MY_CAMERA_PERMISSION_CODE)
{
if (grantResults[0] == PackageManager.PERMISSION_GRANTED)
{
Intent cameraIntent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
startActivityForResult(cameraIntent, CAMERA_REQUEST);
}
else
{
Toast.makeText(this, "Camera Permission Denied..", Toast.LENGTH_LONG).show();
}
}
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == CAMERA_REQUEST && resultCode == Activity.RESULT_OK) {
Bitmap photo = (Bitmap) data.getExtras().get("data");
imageView.setImageBitmap(photo);
}
if (requestCode == PICK_PHOTO_FOR_AVATAR && resultCode == Activity.RESULT_OK) {
if (data == null) {
Log.d("ABC","No Such Image Selected");
return;
}
try {
Uri selectedData=data.getData();
Log.d("ABC","Image Pick-Up");
imageView.setImageURI(selectedData);
InputStream inputStream = getApplicationContext().getContentResolver().openInputStream(selectedData);
Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
Bitmap bmp=MediaStore.Images.Media.getBitmap(getContentResolver(),selectedData);
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch(IOException e){
}
}
}
ActivityResultRegistry是推荐的方法
ComponentActivity现在提供了一个ActivityResultRegistry，它可以让你处理startActivityForResult()+onActivityResult()以及requestPermissions()+onRequestPermissionsResult()流，而无需覆盖你的Activity或Fragment中的方法，通过ActivityResultContract带来了更高的类型安全性，并提供了用于测试这些流的钩子。
强烈建议使用Android 10 Activity 1.2.0-alpha02和Fragment 1.3.0-alpha02中引入的Activity Result api。
将此添加到build.gradle中
def activity_version = "1.2.0-beta01"
// Java language implementation
implementation "androidx.activity:activity:$activity_version"
// Kotlin
implementation "androidx.activity:activity-ktx:$activity_version"
如何使用预建合同
这个新的API具有以下预构建的功能
TakeVideo PickContact GetContent GetContents OpenDocument opendocument OpenDocumentTree CreateDocument 刻度盘 TakePicture RequestPermission RequestPermissions
下面的例子使用了takePicture合约:
private val takePicture = prepareCall(ActivityResultContracts.TakePicture()) { bitmap: Bitmap? ->
// Do something with the Bitmap, if present
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
button.setOnClickListener { takePicture() }
}
So what’s going on here? Let’s break it down slightly. takePicture is just a callback which returns a nullable Bitmap - whether or not it’s null depends on whether or not the onActivityResult process was successful. prepareCall then registers this call into a new feature on ComponentActivity called the ActivityResultRegistry - we’ll come back to this later. ActivityResultContracts.TakePicture() is one of the built-in helpers which Google have created for us, and finally invoking takePicture actually triggers the Intent in the same way that you would previously with Activity.startActivityForResult(intent, REQUEST_CODE).
如何编写自定义合同
一个简单的契约，它接受一个Int作为输入，并返回一个被请求的Activity在结果Intent中返回的字符串。
class MyContract : ActivityResultContract<Int, String>() {
companion object {
const val ACTION = "com.myapp.action.MY_ACTION"
const val INPUT_INT = "input_int"
const val OUTPUT_STRING = "output_string"
}
override fun createIntent(input: Int): Intent {
return Intent(ACTION)
.apply { putExtra(INPUT_INT, input) }
}
override fun parseResult(resultCode: Int, intent: Intent?): String? {
return when (resultCode) {
Activity.RESULT_OK -> intent?.getStringExtra(OUTPUT_STRING)
else -> null
}
}
}
class MyActivity : AppCompatActivity() {
private val myActionCall = prepareCall(MyContract()) { result ->
Log.i("MyActivity", "Obtained result: $result")
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
...
button.setOnClickListener {
myActionCall(500)
}
}
}
查看官方文档了解更多信息。
你需要重写Activity.onActivityResult():
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode == RESULT_CODE_ONE) {
String a = data.getStringExtra("RESULT_CODE_ONE");
}
else if(resultCode == RESULT_CODE_TWO){
// b was clicked
}
else{
}
}
