Android显示TextView文字的倒影效果

　今天记录一下TextView的倒影效果，显示一串文字，然后在文字的下方显示出它的倒影，先上效果图：

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　最重要的就是View中getDrawingCache()方法，该方法可以获取cache中的图像，然后绘制出来。

　　废话不多说，我是想写一个带有倒影的时间，时间可以走动。首先先写一个带有时间走动的View，这个很简单，获取当前时间，然后开启一个线程，隔一秒获取当前时间一次，然后显示在TextView上，当然，我们写控件，就需要继承TextView，代码如下：
　　

package com.alex.reflecttextview;

import java.util.Calendar;

import android.content.Context;
import android.os.Handler;
import android.os.Message;
import android.text.format.DateFormat;
import android.util.AttributeSet;
import android.widget.TextView;

public class TimeView extends TextView {

    private static final int MESSAGE_TIME = 1;

    public TimeView(Context context, AttributeSet attrs) {
        super(context, attrs);
        new TimeThread().start();
    }

    public class TimeThread extends Thread {
        @Override
        public void run() {
            do {
                try {
                    Message msg = new Message();
                    msg.what = MESSAGE_TIME;
                    mHandler.sendMessage(msg);
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            } while (true);
        }
    }

    private Handler mHandler = new Handler() {

        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            switch (msg.what) {
            case MESSAGE_TIME:
                setTime();
                break;

            default:
                break;
            }
        }
    };

    public void setTime() {
        long sysTime = System.currentTimeMillis();
        Calendar calendar = Calendar.getInstance();
        calendar.setTimeInMillis(sysTime);
        String sysTimeStr = DateFormat.format("hh:mm", sysTime).toString();
        if(calendar.get(Calendar.AM_PM) == 0) {
            sysTimeStr += " AM";
        } else {
            sysTimeStr += " PM";
        }
        setText(sysTimeStr.replace("1", " 1"));
    }
}

　现在只需要在布局文件中调用该控件就可以实现一个走动的时间了。

　　第二步就是需要给这个走动的时间加上倒影了，我们就需要写一个控件来继承上面一个时间走动的控件，就可以实现带有倒影的时间走动的View了，下面是带有倒影的代码：
　　

package com.alex.reflecttextview;


import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.LinearGradient;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.PorterDuff.Mode;
import android.graphics.PorterDuffXfermode;
import android.graphics.Shader.TileMode;
import android.util.AttributeSet;

public class ReflectTextView extends TimeView {

    private Matrix mMatrix;
    private Paint mPaint;

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

    private void init() {
        mMatrix = new Matrix();
        mMatrix.preScale(1, -1);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        setMeasuredDimension(getMeasuredWidth(), (int)(getMeasuredHeight()*1.67));
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        int height = getHeight();
        int width = getWidth();
        setDrawingCacheEnabled(true);
        Bitmap originalImage = Bitmap.createBitmap(getDrawingCache());
        Bitmap reflectionImage = Bitmap.createBitmap(originalImage, 0, height/5, width, height/2, mMatrix, false);
        canvas.drawBitmap(reflectionImage, 0, height/3f, null);
        if(mPaint == null)  {
            mPaint = new Paint();   
            LinearGradient shader = new LinearGradient(0, height/2, 0,
                    height, 0x7fffffff, 0x0fffffff, TileMode.CLAMP);
            mPaint.setShader(shader);
            mPaint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));   
        }
        canvas.drawRect(0, height/2f, width, height, mPaint);
    }

    @Override
    protected void onTextChanged(CharSequence text, int start,
            int lengthBefore, int lengthAfter) {
        super.onTextChanged(text, start, lengthBefore, lengthAfter);
        buildDrawingCache();
        postInvalidate();
    }
}

主要功能在onDraw方法里面，先调用setDrawingCacheEnabled(true);让cache可用，然后通过cache创建一个和原图片一样的图像，通过mMatrix.preScale(1, -1);使图片倒过来，调用Bitmap.createBitmap(originalImage, 0, height/5, width, height/2, mMatrix, false);创建一个倒过来的图像，调用canvas.drawBitmap(reflectionImage, 0, height/3f, null);把倒过来的图像画到画布上。通过调用LinearGradient shader = new LinearGradient(0, height/2, 0,
height, 0x7fffffff, 0x0fffffff, TileMode.CLAMP);
mPaint.setShader(shader);
mPaint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));使倒影的图像的颜色渐变，由灰色变为黑色。

　　时间走动时调用buildDrawingCache();
postInvalidate();

　　让倒影从新绘制。

　　调用setMeasuredDimension(getMeasuredWidth(), (int)(getMeasuredHeight()*1.67));设置图像的宽度和高度。

---

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#000000"
    android:paddingTop="@dimen/activity_vertical_margin" >

    <com.alex.reflecttextview.ReflectTextView
            android:id="@+id/timeView"
             android:textSize="@dimen/reflect_size"
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_alignParentBottom="true"
              android:gravity="top|center_horizontal" />
</RelativeLayout>

　然后在Activity中显示这个布局，我把这个控件的字体从新设置了一下，让它显示的方方正正。

---

package com.alex.reflecttextview;

import android.app.Activity;
import android.graphics.Typeface;
import android.os.Bundle;
import android.view.Window;
import android.view.WindowManager;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        final Window win = getWindow();
        win.addFlags(WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED
                | WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD);
        win.addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
                | WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON);
        setContentView(R.layout.activity_main);
        TimeView tv = (TimeView) findViewById(R.id.timeView);
        tv.setTypeface(Typeface.createFromAsset(getAssets(), "fonts/DS-DIGII.TTF"));
    }
}

　好了，就到这里吧。