canvas drawBitmap demo

介绍

简单对图片的放大、缩小、左倾、右倾做出了demo

MainActivity

public class MainActivity extends AppCompatActivity implements View.OnClickListener{
    private Button mBtn_reset,mBtn_left,mBtn_right,mBtnzoomin,mBtnzoomout;
    private MyView myView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        bindViews();//init button so on
    }

    private void bindViews(){
        mBtn_reset = (Button) findViewById(R.id.btn_reset);
        mBtn_left = (Button) findViewById(R.id.btn_left);
        mBtn_right = (Button) findViewById(R.id.btn_right);
        mBtnzoomin = (Button) findViewById(R.id.btn_zoomin);
        mBtnzoomout = (Button) findViewById(R.id.btn_zoomout);

        myView = (MyView) findViewById(R.id.myView);
//        myView = new MyView(this);

        mBtn_reset.setOnClickListener(this);
        mBtn_left.setOnClickListener(this);
        mBtn_right.setOnClickListener(this);
        mBtnzoomin.setOnClickListener(this);
        mBtnzoomout.setOnClickListener(this);

    }
    @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.btn_reset:
                myView.setMethod(0);
                break;
            case R.id.btn_left:
                myView.setMethod(1);
                break;
            case R.id.btn_right:
                myView.setMethod(2);
                break;
            case R.id.btn_zoomin:
                myView.setMethod(3);
                break;
            case R.id.btn_zoomout:
                myView.setMethod(4);
                break;
            default:
                Log.i(this.getClass().getSimpleName(),"switch default");

        }
    }
}

MyView

public class MyView extends View {
    private final String TAG = "MyView";
    private Bitmap mBitmap;
    private Matrix matrix =  new Matrix();
    private float sx = 0.0f;//倾斜度
    private int mWidth,mHeight;//位宽高
    private float mScale = 1.0f;//缩放比例
    private int method = 0;

    public MyView(Context context) {
        this(context, null);
    }

    public MyView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

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

    private void init() {
        Log.e(TAG, "init");
        mBitmap = BitmapFactory.decodeResource(getResources(), R.raw.img_meizi);
        mWidth = mBitmap.getWidth();
        mHeight = mBitmap.getHeight();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        switch(method){
            case 0:
                matrix.reset();
                resetValue();
                break;
            case 1:
                sx += 0.1;
                matrix.setSkew(sx,0);
                break;
            case 2:
                sx -= 0.1;
                matrix.setSkew(sx,0);
                break;
            case 3:
                if(mScale < 2.0){
                    mScale += 0.1;
                }
                matrix.setScale(mScale,mScale);
                break;
            case 4:
                if(mScale > 0.5){
                    mScale -= 0.1;
                }
                matrix.setScale(mScale,mScale);
                break;
            default:
                Log.i(this.getClass().getSimpleName(),"switch default");
        }
        //根据原始位图创新新图片
        Bitmap bitmap = Bitmap.createBitmap(mBitmap,0,0, mWidth, mHeight, matrix,true);
        canvas.drawBitmap(bitmap, matrix,null);//绘制新图
    }

    private void resetValue() {
        mScale = 1.0f;
        sx = 0.0f;
    }

    public void setMethod(int i){
        method = i;
        postInvalidate();
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <LinearLayout
        android:id="@+id/ly_bar"
        android:layout_width="match_parent"
        android:layout_height="64dp"
        android:layout_alignParentBottom="true">
        <Button
            android:id="@+id/btn_reset"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:text="重置" />

        <Button
            android:id="@+id/btn_left"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:text="左倾" />

        <Button
            android:id="@+id/btn_right"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:text="右倾" />

        <Button
            android:id="@+id/btn_zoomin"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:text="放大" />

        <Button
            android:id="@+id/btn_zoomout"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:text="缩小" />
    </LinearLayout>

        <com.kang.test.view.MyView
            android:id="@+id/myView"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_above="@id/ly_bar"/>

</RelativeLayout>