安卓 (Android) 一张图片实现按下效果的Button[亲测有效]

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在Android开发过程中，一定会用到带图片的按钮，传统方法是UI出两张图，一张正常状态，一张按下状态。其实多数时候，按钮按下的效果就是正常状态的图片改变一下亮度，废话少说，直接上代码。

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.Canvas;
import android.graphics.ColorMatrix;
import android.graphics.ColorMatrixColorFilter;
import android.graphics.Paint;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.StateListDrawable;
import android.util.AttributeSet;
import android.widget.Button;

/**
 * 单张图片实现按下效果的Button
 *
 * @author CharlesRich
 * @email 18602438878@qq.com
 * @mobile 18602438878
 * @create 2020-02-10 18:55
 */
public class ImageButton extends Button {
    private Context context;

    public ImageButton(Context context) {
        super(context);
        this.context = context;
        init();
    }

    public ImageButton(Context context, AttributeSet attrs) {
        super(context, attrs);
        this.context = context;
        init();
    }

    public ImageButton(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        this.context = context;
        init();
    }

    private void init() {
        setBackgroundDrawable(newSelector());
    }

    /**
     * 传入改变亮度前的bitmap，返回改变亮度后的bitmap
     *
     * @param bitmap
     * @return
     */
    private Drawable changeBrightnessBitmap(Bitmap bitmap) {
        Bitmap bmp = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(),
                Config.ARGB_8888);
        int brightness = 60 - 127;
        ColorMatrix cMatrix = new ColorMatrix();
        cMatrix.set(new float[]{1, 0, 0, 0, brightness, 0, 1,
                0, 0, brightness,/** 改变亮度 */
                0, 0, 1, 0, brightness, 0, 0, 0, 1, 0});
        Paint paint = new Paint();
        paint.setColorFilter(new ColorMatrixColorFilter(cMatrix));
        Canvas canvas = new Canvas(bmp);
        /** 在Canvas上绘制一个Bitmap */
        canvas.drawBitmap(bitmap, 0, 0, paint);
        return new BitmapDrawable(bmp);
    }

    /**
     * 设置Selector
     */
    private StateListDrawable newSelector() {
        StateListDrawable bg = new StateListDrawable();
        Drawable normal = getBackground();
        Drawable pressed = changeBrightnessBitmap(((BitmapDrawable) getBackground()).getBitmap());
        /** View.PRESSED_ENABLED_STATE_SET */
        bg.addState(new int[]{android.R.attr.state_pressed, android.R.attr.state_enabled}, pressed);
        /** View.ENABLED_STATE_SET */
        bg.addState(new int[]{android.R.attr.state_enabled}, normal);
        /** View.EMPTY_STATE_SET */
        bg.addState(new int[]{}, normal);
        return bg;
    }

}

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