Android放大鏡的實(shí)現(xiàn)代碼

2020-04-11 11:56:22

字體：大中小

供稿：網(wǎng)友

快三個(gè)月了沒寫博客了，因?yàn)楣ぷ髡{(diào)動，很多經(jīng)驗(yàn)、心得都沒有時(shí)間記錄下來。現(xiàn)在時(shí)間稍微充裕了點(diǎn)，我會盡量抽時(shí)間將之前想寫而沒寫的東西補(bǔ)上。進(jìn)入正題。
去年某個(gè)時(shí)候，我偶然看到一篇文章，講android里面放大鏡的實(shí)現(xiàn)。文章很亂，沒有格式，基本上屬于看不下去的那種。雖然體裁很有意思，但是我也沒有足夠的內(nèi)力把它看完。不過看到一句關(guān)鍵的話，說是使用帶圓形的Drawable。這句話就夠了，他下面寫的一堆東西我也懶得看，于是就自己開始嘗試，然后就做出來了。現(xiàn)在代碼貼出來分享。
Java代碼

復(fù)制代碼代碼如下:

package chroya.demo.magnifier;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Shader.TileMode;
import android.graphics.drawable.ShapeDrawable;
import android.graphics.drawable.shapes.OvalShape;
import android.view.MotionEvent;
import android.view.View;

/**
* 放大鏡實(shí)現(xiàn)方式1
* @author chroya
*
*/
public class ShaderView extends View{
private Bitmap bitmap;
private ShapeDrawable drawable;
//放大鏡的半徑
private static final int RADIUS = 80;
//放大倍數(shù)
private static final int FACTOR = 3;
private Matrix matrix = new Matrix();

public ShaderView(Context context) {
  super(context);
  Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.show);
  bitmap = bmp;
  BitmapShader shader = new BitmapShader(
    Bitmap.createScaledBitmap(bmp, bmp.getWidth()*FACTOR,
      bmp.getHeight()*FACTOR, true), TileMode.CLAMP, TileMode.CLAMP);
  //圓形的drawable
  drawable = new ShapeDrawable(new OvalShape());
  drawable.getPaint().setShader(shader);
  drawable.setBounds(0, 0, RADIUS*2, RADIUS*2);
}

@Override
public boolean onTouchEvent(MotionEvent event) {
  final int x = (int) event.getX();
  final int y = (int) event.getY();
  //這個(gè)位置表示的是，畫shader的起始位置
  matrix.setTranslate(RADIUS-x*FACTOR, RADIUS-y*FACTOR);
  drawable.getPaint().getShader().setLocalMatrix(matrix);
  //bounds，就是那個(gè)圓的外切矩形
  drawable.setBounds(x-RADIUS, y-RADIUS, x+RADIUS, y+RADIUS);
  invalidate();
  return true;
}

@Override
public void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  canvas.drawBitmap(bitmap, 0, 0, null);
  drawable.draw(canvas);
}
}

基本原理就是使用ShapeDrawable構(gòu)造一個(gè)圓形的drawable，然后它的paint的shader設(shè)置為將要放大的圖片，然后就是簡單的位置移動問題了。放大鏡的半徑和放大倍數(shù)都可以在代碼里面修改，代碼都有注釋，應(yīng)該很好理解了。

不過，一個(gè)問題如果只有一種解決方法的話，那未免有點(diǎn)令人沮喪，想玩點(diǎn)另類的都不行。
玩程序就得玩出個(gè)性，玩出激情。哈哈，廢話太多，切回正題。

再來看看放大鏡的另外一種實(shí)現(xiàn)吧 ^-^
Java代碼

復(fù)制代碼代碼如下:

package chroya.demo.magnifier;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Path;
import android.graphics.Path.Direction;
import android.view.MotionEvent;
import android.view.View;

/**
* 放大鏡實(shí)現(xiàn)方式2
* @author chroya
*
*/
public class PathView extends View{
private Path mPath = new Path();
private Matrix matrix = new Matrix();
private Bitmap bitmap;
//放大鏡的半徑
private static final int RADIUS = 80;
//放大倍數(shù)
private static final int FACTOR = 2;
private int mCurrentX, mCurrentY;

public PathView(Context context) {
  super(context);
  mPath.addCircle(RADIUS, RADIUS, RADIUS, Direction.CW);
  matrix.setScale(FACTOR, FACTOR);

  bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.show);
}

@Override
public boolean onTouchEvent(MotionEvent event) {
  mCurrentX = (int) event.getX();
  mCurrentY = (int) event.getY();

  invalidate();
  return true;
}

@Override
public void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  //底圖
  canvas.drawBitmap(bitmap, 0, 0, null);
  //剪切
  canvas.translate(mCurrentX - RADIUS, mCurrentY - RADIUS);
  canvas.clipPath(mPath);
  //畫放大后的圖
  canvas.translate(RADIUS-mCurrentX*FACTOR, RADIUS-mCurrentY*FACTOR);
  canvas.drawBitmap(bitmap, matrix, null);
}
}