不推荐使用OnActivityResult方法，替代方案是什么？

Question

我最近发现onActivityResult是不推荐的。我们该怎么处理？

有什么替代方案吗？

Answer 1

developer.android.com提供了基本培训。

下面是一个如何用新代码转换现有代码的示例：

老办法：

    public void openSomeActivityForResult() {
        Intent intent = new Intent(this, SomeActivity.class);
        startActivityForResult(intent, 123);
    }

    @Override
    protected void onActivityResult (int requestCode, int resultCode, Intent data) {
        if (resultCode == Activity.RESULT_OK && requestCode == 123) {
            doSomeOperations();
        }
    }

    // You can do the assignment inside onAttach or onCreate, i.e, before the activity is displayed
    ActivityResultLauncher<Intent> someActivityResultLauncher = registerForActivityResult(
            new ActivityResultContracts.StartActivityForResult(),
            new ActivityResultCallback<ActivityResult>() {
                @Override
                public void onActivityResult(ActivityResult result) {
                    if (result.getResultCode() == Activity.RESULT_OK) {
                        // There are no request codes
                        Intent data = result.getData();
                        doSomeOperations();
                    }
                }
            });

    public void openSomeActivityForResult() {
        Intent intent = new Intent(this, SomeActivity.class);
        someActivityResultLauncher.launch(intent);
    }

var resultLauncher = registerForActivityResult(StartActivityForResult()) { result ->
    if (result.resultCode == Activity.RESULT_OK) {
        // There are no request codes
        val data: Intent? = result.data
        doSomeOperations()
    }
}

fun openSomeActivityForResult() {
    val intent = Intent(this, SomeActivity::class.java)
    resultLauncher.launch(intent)
}

import android.content.Intent;
import androidx.activity.result.ActivityResult;
import androidx.activity.result.ActivityResultCaller;
import androidx.activity.result.ActivityResultLauncher;
import androidx.activity.result.contract.ActivityResultContract;
import androidx.activity.result.contract.ActivityResultContracts;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;

public class BetterActivityResult<Input, Result> {
    /**
     * Register activity result using a {@link ActivityResultContract} and an in-place activity result callback like
     * the default approach. You can still customise callback using {@link #launch(Object, OnActivityResult)}.
     */
    @NonNull
    public static <Input, Result> BetterActivityResult<Input, Result> registerForActivityResult(
            @NonNull ActivityResultCaller caller,
            @NonNull ActivityResultContract<Input, Result> contract,
            @Nullable OnActivityResult<Result> onActivityResult) {
        return new BetterActivityResult<>(caller, contract, onActivityResult);
    }

    /**
     * Same as {@link #registerForActivityResult(ActivityResultCaller, ActivityResultContract, OnActivityResult)} except
     * the last argument is set to {@code null}.
     */
    @NonNull
    public static <Input, Result> BetterActivityResult<Input, Result> registerForActivityResult(
            @NonNull ActivityResultCaller caller,
            @NonNull ActivityResultContract<Input, Result> contract) {
        return registerForActivityResult(caller, contract, null);
    }

    /**
     * Specialised method for launching new activities.
     */
    @NonNull
    public static BetterActivityResult<Intent, ActivityResult> registerActivityForResult(
            @NonNull ActivityResultCaller caller) {
        return registerForActivityResult(caller, new ActivityResultContracts.StartActivityForResult());
    }

    /**
     * Callback interface
     */
    public interface OnActivityResult<O> {
        /**
         * Called after receiving a result from the target activity
         */
        void onActivityResult(O result);
    }

    private final ActivityResultLauncher<Input> launcher;
    @Nullable
    private OnActivityResult<Result> onActivityResult;

    private BetterActivityResult(@NonNull ActivityResultCaller caller,
                                 @NonNull ActivityResultContract<Input, Result> contract,
                                 @Nullable OnActivityResult<Result> onActivityResult) {
        this.onActivityResult = onActivityResult;
        this.launcher = caller.registerForActivityResult(contract, this::callOnActivityResult);
    }

    public void setOnActivityResult(@Nullable OnActivityResult<Result> onActivityResult) {
        this.onActivityResult = onActivityResult;
    }

    /**
     * Launch activity, same as {@link ActivityResultLauncher#launch(Object)} except that it allows a callback
     * executed after receiving a result from the target activity.
     */
    public void launch(Input input, @Nullable OnActivityResult<Result> onActivityResult) {
        if (onActivityResult != null) {
            this.onActivityResult = onActivityResult;
        }
        launcher.launch(input);
    }

    /**
     * Same as {@link #launch(Object, OnActivityResult)} with last parameter set to {@code null}.
     */
    public void launch(Input input) {
        launch(input, this.onActivityResult);
    }

    private void callOnActivityResult(Result result) {
        if (onActivityResult != null) onActivityResult.onActivityResult(result);
    }
}

public class BaseActivity extends AppCompatActivity {
    protected final BetterActivityResult<Intent, ActivityResult> activityLauncher = BetterActivityResult.registerActivityForResult(this);
}

之后，您可以简单地从任何子活动中启动一个活动，如下所示：

    public void openSomeActivityForResult() {
        Intent intent = new Intent(this, SomeActivity.class);
        activityLauncher.launch(intent, result -> {
            if (result.getResultCode() == Activity.RESULT_OK) {
                // There are no request codes
                Intent data = result.getData();
                doSomeOperations();
            }
        })
    }

由于可以将回调函数与意图一起设置，因此可以将其用于任何活动。

同样，您也可以使用其他两个构造函数来使用其他活动契约。