博客

作为应届生，刚入职公司，现在想从零开始学习一个全新的领域——音视频开发，仅此记录一下。

ImageView绘制图片

这种常规的绘制图片方式，简单粗暴。

        String pathName = Environment.getExternalStorageDirectory().getAbsolutePath()
                + "/Audio/1.png";
        binding.btBitmap.setOnClickListener(view -> {
            Bitmap bitmap = BitmapFactory.decodeFile(pathName);
            binding.imageView.setImageBitmap(bitmap);
        });

SurFaceView绘制图片

使用surFaceView可以在独立的线程绘制UI，不会引起UI线程的卡帧。底层实现了双缓冲机制，绘制效率较高。

xml代码

        <SurfaceView
            android:id="@+id/surface"
            android:layout_width="200dp"
            android:layout_height="200dp"
            android:visibility="invisible"
            android:layout_marginBottom="10dp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent" />

java代码

        binding.surface.getHolder().addCallback(new SurfaceHolder.Callback() {
            @Override
            public void surfaceCreated(@NonNull SurfaceHolder surfaceHolder) {
                if (surfaceHolder == null) {
                    return;
                }
                Paint paint = new Paint();
                //去锯齿
                paint.setAntiAlias(true);
                //描边
                paint.setStyle(Paint.Style.STROKE);

                Bitmap bitmap = BitmapFactory.decodeFile(pathName);
                //锁定surface画布
                Canvas canvas = surfaceHolder.lockCanvas();
                canvas.drawBitmap(bitmap, 0, 0, paint);
                surfaceHolder.unlockCanvasAndPost(canvas);
            }

            @Override
            public void surfaceChanged(@NonNull SurfaceHolder surfaceHolder, int i, int i1, int i2) {

            }

            @Override
            public void surfaceDestroyed(@NonNull SurfaceHolder surfaceHolder) {

            }
        });

自定义View绘制

使用自定义view会更加灵活，当然如果只绘制一张普通的图片其实，这种方式我觉得并不方便。

public class JImageView extends View {

    Paint paint = new Paint();
    Bitmap bitmap;
    String pathName = Environment.getExternalStorageDirectory().getAbsolutePath()
            + "/Audio/1.png";

    public JImageView(Context context) {
        super(context);
        init();
    }

    public JImageView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public JImageView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    protected void init(){
        paint.setAntiAlias(true);
        paint.setStyle(Paint.Style.STROKE);
        bitmap = BitmapFactory.decodeFile(pathName);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if (bitmap !=null){
            canvas.drawBitmap(bitmap,0,0,paint);
        }
    }
}

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