Android截图开发工具

ScreenshotUtil实现

最近多次在项目中用到截图功能，于是封装了一个截图工具，使用MediaProjection实现截图，权限申请使用了RxActivityResult。
使用方法：

1. 在Application中注册

public class MyApp  extends Application {

    @Override public void onCreate() {
        super.onCreate();
        ScreenshotUtil.register(this);
    }
}

2. 在on方法中传入Activity 对象，在subscribe中处理截图的结果Bitmap

ScreenshotUtil.on(this).takeScreenshot().subscribe(bitmap -> { if (bitmap == null) {
    Log.e(TAG, "Bitmap is null.");
} else {
     mImageView.setImageBitmap(bitmap);
}});

Github: https://github.com/MissMidou/Android-Develop-Tool

RxActivityResult 实现原理

在startActivityForResult 时，需要在onActivityResult 中处理返回结果，而使用RxActivityResult，可以不用重写onActivityResult来直接处理返回结果，代码简介清晰。

Github: https://github.com/VictorAlbertos/RxActivityResult
使用范例：

public class SampleApp extends Application {

    @Override public void onCreate() {
        super.onCreate();
        RxActivityResult.register(this);
    }
}

RxActivityResult.register(this);用于判断在顶层的Activity的生命周期，用这个Activity打开目标Activity

Intent takePhoto = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);

RxActivityResult.on(this).startIntent(takePhoto)
        .subscribe(result -> {
            Intent data = result.data();
            int resultCode = result.resultCode();
            // the requestCode using which the activity is started can be received here.
            int requestCode = result.requestCode();

            if(requestCode == YourActivity.YOUR_REQUEST_CODE)
            {
                // Do Something
            }

            if (resultCode == RESULT_OK) {
                result.targetUI().showImage(data);
            } else {
                result.targetUI().printUserCanceled();
            }
        });

on()返回一个Builder 对象,Builder中创建一个PublishSubject实例，PublishSubject与普通Observable相比，Observable是订阅时立即触发订阅事件,而PublishSubject可以在任意时刻调用onNext,onComplete方法触发订阅事件，观察者在订阅之后便可以收到事件，这里在onActivityResult返回结果后，触发订阅事件

    public static <T extends Activity> Builder<T> on(T activity) {
        return new Builder<T>(activity);
    }
    public static class Builder<T> {
        final Class clazz;
        final PublishSubject<Result<T>> subject = PublishSubject.create();
        private final boolean uiTargetActivity;
        ... ...
    }

startIntent（）调用startHolderActivity，通过打开一个HolderActivity，然后在HolderActivity中打开目标Activity,并在onActivityResult处理结果

        private Observable<Result<T>> startHolderActivity(Request request, @Nullable OnPreResult onPreResult) {

            OnResult onResult = uiTargetActivity ? onResultActivity() : onResultFragment();
            request.setOnResult(onResult);
            request.setOnPreResult(onPreResult);

            HolderActivity.setRequest(request);
            //getOLiveActivity找到顶层Activity，因为在Fragment中打开的时候需要Activity
            activitiesLifecycle.getOLiveActivity().subscribe(new Consumer<Activity>() {
                @Override
                public void accept(Activity activity) throws Exception {
                    activity.startActivity(new Intent(activity, HolderActivity.class)
                            .addFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION));
                }
            });

            return subject;
        }

HolderActivity打开目标Activity后，onActivityResult中保存结果并finish,然后onDestroy 中发射订阅事件
HolderActivity.java

    @Override
    protected void onDestroy() {
        super.onDestroy();
        if (onResult != null)
            onResult.response(requestCode, resultCode, data);
    }

        private OnResult onResultActivity() {
            return new OnResult() {
                @Override
                public void response(int requestCode, int resultCode, Intent data) {
                    if (activitiesLifecycle.getLiveActivity() == null) return;

                    //If true it means some other activity has been stacked as a secondary process.
                    //Wait until the current activity be the target activity
                    if (activitiesLifecycle.getLiveActivity().getClass() != clazz) {
                        return;
                    }

                    T activity = (T) activitiesLifecycle.getLiveActivity();
                    subject.onNext(new Result<>(activity, requestCode, resultCode, data));
                    subject.onComplete();
                }

                @Override
                public void error(Throwable throwable) {
                    subject.onError(throwable);
                }
            };
        }

参考文档：

http://gank.io/post/560e15be2dca930e00da1083#toc_17