大家如果喜欢我的博客,请关注一下我的微博,请点击这里(http://weibo.com/kifile),谢谢

转载请标明出处(http://blog.csdn.net/kifile),再次感谢

在开发过程中,单纯的 Drawable 文件无法满足我们对整个项目的需求.

有时候在制作过场动画的时候,我们会希望将一个 Drawable 文件以中心为基准,按顺时针慢慢显示出来,可是 Android 并没有为我们提供一个工具类,我们也不希望为了单纯的显示整张图片而去制作 N 张图片以满足过场动画的需求,那么我们这个时候只能考虑对 Drawable 的绘画区域做裁剪,让他只显示扇形区域的大小,以满足我们的需求.

幸而, Android 本身有一个 ClipDrawable 类,这个类让我们能够轻松的显示进度条加载进度,本次我们也将根据这个类来创建一个类似的代码

先送上具体源码,然后我们会详细分析一下裁剪显示区域的原理

/*
 * Copyright (C) 2014 Kifile(kifile@kifile.com)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.kifile.graphics;

import android.content.res.ColorStateList;
import android.graphics.*;
import android.graphics.drawable.Drawable;

/**
 * Created by kifile on 14/10/31.
 */
public class SectorDrawable extends Drawable implements Drawable.Callback {
    private Drawable mDrawable;
    private Path mPath = new Path();
    private float mPercent;

    public SectorDrawable(Drawable drawable) {
        this.mDrawable = drawable;
        if (drawable != null) {
            drawable.setCallback(this);
        }
    }

    @Override
    public int getChangingConfigurations() {
        return super.getChangingConfigurations() | mDrawable.getChangingConfigurations();
    }

    @Override
    public boolean getPadding(Rect padding) {
        return mDrawable.getPadding(padding);
    }

    @Override
    public boolean setVisible(boolean visible, boolean restart) {
        mDrawable.setVisible(visible, restart);
        return super.setVisible(visible, restart);
    }

    @Override
    public void draw(Canvas canvas) {
        mPath.reset();
        RectF rect = new RectF(getBounds());
        double radius = Math.pow(Math.pow(rect.right, 2) + Math.pow(rect.bottom, 2), 0.5);
        mPath.moveTo(rect.right / 2, rect.bottom / 2);
        mPath.lineTo(rect.right / 2, 0);
        if (mPercent > 0.125f) {
            mPath.lineTo(rect.right, 0);
        }
        if (mPercent > 0.375f) {
            mPath.lineTo(rect.right, rect.bottom);
        }
        if (mPercent > 0.625f) {
            mPath.lineTo(0, rect.bottom);
        }
        if (mPercent > 0.875f) {
            mPath.lineTo(0, 0);
        }
        mPath.lineTo((float) (rect.right / 2 + radius * Math.sin(Math.PI * 2 * mPercent)),
                (float) (rect.bottom / 2 - radius * Math.cos(Math.PI * 2 * mPercent)));
        mPath.close();
        if (mPercent >= 0 && mPercent <= 1) {
            canvas.save();
            canvas.clipPath(mPath);
            mDrawable.draw(canvas);
            canvas.restore();
        }
    }

    @Override
    public void setAlpha(int alpha) {
        mDrawable.setAlpha(alpha);
    }

    @Override
    public int getAlpha() {
        return mDrawable.getAlpha();
    }

    @Override
    public void setColorFilter(ColorFilter cf) {
        mDrawable.setColorFilter(cf);
    }

    @Override
    public void setTintList(ColorStateList tint) {
        mDrawable.setTintList(tint);
    }

    @Override
    public void setTintMode(PorterDuff.Mode tintMode) {
        mDrawable.setTintMode(tintMode);
    }

    @Override
    public int getOpacity() {
        // TODO Auto-generated method stub
        return mDrawable.getOpacity();
    }

    @Override
    public boolean isStateful() {
        // TODO Auto-generated method stub
        return mDrawable.isStateful();
    }

    @Override
    protected boolean onStateChange(int[] state) {
        return mDrawable.setState(state);
    }

    @Override
    protected boolean onLevelChange(int level) {
        mDrawable.setLevel(level);
        invalidateSelf();
        return true;
    }

    @Override
    protected void onBoundsChange(Rect bounds) {
        mDrawable.setBounds(bounds);
    }

    @Override
    public int getIntrinsicHeight() {
        return mDrawable.getIntrinsicHeight();
    }

    @Override
    public int getIntrinsicWidth() {
        return mDrawable.getIntrinsicWidth();
    }

    /**
     * 显示的区域范围
     *
     * @param percent 0至1
     */
    public void setPercent(float percent) {
        if (percent > 1) {
            percent = 1;
        } else if (percent < 0) {
            percent = 0;
        }
        if (percent != mPercent) {
            this.mPercent = percent;
            invalidateSelf();
        }
    }

    @Override
    public void invalidateDrawable(Drawable who) {
        final Callback callback = getCallback();
        if (callback != null) {
            callback.invalidateDrawable(this);
        }
    }

    @Override
    public void scheduleDrawable(Drawable who, Runnable what, long when) {
        final Callback callback = getCallback();
        if (callback != null) {
            callback.scheduleDrawable(this, what, when);
        }
    }

    @Override
    public void unscheduleDrawable(Drawable who, Runnable what) {
        final Callback callback = getCallback();
        if (callback != null) {
            callback.unscheduleDrawable(this, what);
        }
    }

}

首先大家先来看一张图:

黑色部分为画布区域, w 为宽度, h 为高度, radius 为中心点到角的距离,上图中为我们标明了9个重要的坐标点位置,接下来我们将介绍如何根据旋转角度来设置选定区域范围

首先我们先规定扇形区域的起始位置为(w/2,0)处,旋转方式为顺时针旋转,并假设有一 A 点为扇形旋转区域另一边的,长度为 radius(关于 radius 的定义请参看上面) 的边角

(1)当旋转区域不超过1/8时,扇形区域的绘制如下:

那么由图可知,我们需要裁减的区域为上图中的蓝色区域即可

(2)对于旋转区域超过1/8,不超过3/8时,扇形区域绘制如下:

由图可知,我们需要裁减的蓝色区域,可由,中心点,起始点,右上角和 A 点连线组成

(3)对于旋转区域超过3/8不超过5/8时,扇形区域绘制如下:

由图可知,我们需要裁减的蓝色区域,可由,中心点,起始点,右上角,右下角和 A 点连线组成

(4)对于超过5/8,不超过7/8的部分,裁剪区域如下:

(5)对于超过7/8的部分而言,裁减区域如下

因此我们可以通过判断设定的显示区域,动态对画布进行裁减,以达到显示扇形区域的目的

具体的设置代码,就在顶部,大家如果有兴趣可以详细看看,接下来我们将查看如何正确使用 SectorDrawable

ImageView img = (ImageView) findViewById(R.id.sector_img);
        mDrawable = new SectorDrawable(img.getDrawable());
        img.setImageDrawable(mDrawable);

当我们需要调用代码进行区域显示设置时,使用

mDrawable.setPercent(percent);

/*
 * Copyright (C) 2014 Kifile(kifile@kifile.com)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.kifile.sample.app;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ImageView;
import com.kifile.graphics.SectorDrawable;


public class MainActivity extends ActionBarActivity {
    private SectorDrawable mDrawable;

    private Handler mHandler = new Handler() {
        private float percent;

        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            if (percent <= 1) {
                percent += 0.01;
            } else {
                percent = 0;
                return;
            }
            mDrawable.setPercent(percent);
            Log.i("this",String.valueOf(percent));
            sendEmptyMessageDelayed(0, 10);
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ImageView img = (ImageView) findViewById(R.id.sector_img);
        mDrawable = new SectorDrawable(img.getDrawable());
        img.setImageDrawable(mDrawable);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            mHandler.sendEmptyMessage(0);
            return true;
        }

        return super.onOptionsItemSelected(item);
    }


}

好了,本次博客就到这里了,谢谢大家的翻阅

简单几步教你实现对 Drawable 的扇形区域剪切显示