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音视频任务1

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跟着大神的步骤一步一步做，加油！
任务列表：http://blog.51cto.com/ticktick/1956269

在 Android 平台绘制一张图片，使用至少 3 种不同的 API，ImageView，SurfaceView，自定义 View
imageView和surfaceView，为了方便都是直接在activity里面写的函数，直接在onCreateView里面调用

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import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Rect;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.widget.ImageView;

public class MainActivity extends AppCompatActivity {

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

    void displayImg(){
        final ImageView iv = findViewById(R.id.iv_lu);
        //1
//        iv.setImageResource(R.mipmap.wechatimg1);

        //2
//        Drawable drawable = getResources().getDrawable(R.mipmap.wechatimg1, null);
//        iv.setImageDrawable(drawable);
        //3
        Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.wechatimg1);
        iv.setImageBitmap(bitmap);
    }

    void displaySurfaceView(){
        final SurfaceView sv = findViewById(com.example.lujianyun.va.R.id.sv_lu);

        final SurfaceHolder holder = sv.getHolder();
        final Thread t = new Thread(new Runnable() {
            @Override
            public void run() {
                Canvas canvas = holder.lockCanvas();
                Bitmap bitmap = BitmapFactory.decodeResource(getResources(), com.example.lujianyun.va.R.mipmap.wechatimg1);
                canvas.drawBitmap(bitmap, 0, 0, null);
                holder.unlockCanvasAndPost(canvas);
                holder.lockCanvas(new Rect(0,0,0,0));
                holder.unlockCanvasAndPost(canvas);
            }
        });

        holder.addCallback(new SurfaceHolder.Callback() {
            @Override
            public void surfaceCreated(SurfaceHolder holder) {
                t.start();
            }

            @Override
            public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

            }

            @Override
            public void surfaceDestroyed(SurfaceHolder holder) {

            }
        });



    }
}

自定义view

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public class DrawView extends View {

    String TAG = "DrawView";
    Bitmap bitmap;
    Bitmap orginBitmap;
    boolean bitmapFinished = false;

    public DrawView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        orginBitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.wechatimg1);


    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        if (!bitmapFinished) { //由于onmeasure要多次调用，所以创建对象的工作只做一次，防止耗时
            int w = MeasureSpec.getSize(widthMeasureSpec);
            int h = MeasureSpec.getSize(heightMeasureSpec);
            bitmap = Bitmap.createScaledBitmap(orginBitmap, w, h, false); 
            bitmapFinished = true;
        }
        super.onMeasure(widthMeasureSpec,heightMeasureSpec);
    }

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

}

布局文件：

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<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="300dp"
    android:layout_height="300dp"
    tools:context=".MainActivity"
    android:clipChildren="false">

    <ImageView
        android:id="@+id/iv_lu"
        android:visibility="gone"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <SurfaceView
        android:id="@+id/sv_lu"
        android:visibility="gone"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <com.example.lll.va.DrawView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>