Android 图片特效如何实现及总结

package lesson10_fragmentfordata.myapplication;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.util.AttributeSet;
import android.view.KeyEvent;
import android.view.View;

/**
 * 图像特效的演示
 */

public class MyView extends View {


  //定义Bitmap对象
  Bitmap bitmap;
  //创建矩阵对象
  Matrix matrix = new Matrix();

  //宽和高
  int width, height;

  //缩放比例
  float scale = 1f;

  //图像的状态是缩放还是旋转
  Boolean isScale = false;
  //判断是否旋转
  Boolean istRotate = false;

  //x轴方向倾斜的角度
  private float sx;
  //旋转的角度
  private float degress;

  //重写俩个构造方法
  public MyView(Context context) {
    super(context);
    initView();
  }

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

  /**
   * 初始化数据
   */
  private void initView() {
    //获取位图  bitmap=getContext().getResources().getDrawable(R.mipmap.img01);
    bitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.a3);
    //获取宽和高
    width = bitmap.getWidth();
    height = bitmap.getHeight();
    //使当前的视图获取焦点
    this.setFocusable(true);
  }

  /**
   * 重写onDraw重绘的方法
   */
  @Override
  protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    matrix.reset();//重置
    if (isScale) {
      //伸缩状态
      matrix.setScale(scale, scale);
    } else {
      //倾斜状态
      matrix.setSkew(sx, 0);
    }

    if (istRotate) {
      //顺时针旋转30度
      matrix.setRotate(degress,0.5f*width,0.5f*height);
    }
    //根据原始位图和Matrix创建新图片
    Bitmap bit = Bitmap.createBitmap(bitmap, 0, 0, width, height, matrix, true);
    //从新绘制位图
    canvas.drawBitmap(bit, matrix, null);

  }

  /**
   * 键盘控制的逻辑
   */
  @Override
  public boolean onKeyDown(int keyCode, KeyEvent event) {
    switch (keyCode) {
      case KeyEvent.KEYCODE_A://点击A向左倾斜
        isScale = false;
        istRotate=false;
        sx -= 0.1;
        invalidate();//重绘
        break;
      case KeyEvent.KEYCODE_D://点击D向右倾斜
        isScale = false;
        istRotate=false;
        sx += 0.1;
        invalidate();//重绘
        break;
      case KeyEvent.KEYCODE_W://点击W图像变大
        isScale = true;
        istRotate=false;
        scale += 0.1;
        invalidate();//重绘
        break;
      case KeyEvent.KEYCODE_S://点击S图像变小
        isScale = true;
        istRotate=false;
        scale -= 0.1;
        invalidate();//重绘
        break;
      case KeyEvent.KEYCODE_X://点击x图像顺时针旋转30度
        istRotate = true;
        degress += 30;
        invalidate();//重绘
        break;

    }
    return super.onKeyDown(keyCode, event);
  }
}

public class MainActivity extends Activity {


  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(new MyView(this));
  }
}