TextureView 的使用

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在上文中介绍了 SurfaceView, TextureView 和普通的 View 的区别。现在介绍SurfaceView 和 TextureView的区别。

TextureView 适用于 Android 4.0 和之后的版本，在很多的情况下可以顺便作为 SurfaceView 的替代品来使用。TextureView 的行为更像传统的 View，可以对绘制在它上面的内容实现动画和变换。但要求运行它的环境是硬件加速的，这可能会导致某些应用程序的兼容性问题。应用程序在 SDK 为 11或以上的版本时，默认启动了硬件加速。（如果需要禁用硬件加速可在 AndroidManifest.xml 文件中的 <activity> 或整个 <application> 标签中添加 android:hardwareAccelerated="false"，即可。）

下面这个示例是从上一篇博客中的示例修改而来，效果如下：

content_main.xml :

<?xml version="1.0" encoding="utf-8"?><FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:app="http://schemas.android.com/apk/res-auto"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    app:layout_behavior="@string/appbar_scrolling_view_behavior"    tools:context="com.crazy.textureviewtest.MainActivity"    tools:showIn="@layout/activity_main">    <Button        android:id="@+id/button_transform"        android:text="旋转"        android:layout_width="match_parent"        android:layout_height="wrap_content" />    <TextureView        android:id="@+id/surface"        android:layout_gravity="center"        android:layout_width="300dp"        android:layout_height="300dp" /></FrameLayout>

Mainactivity.java :

package com.crazy.textureviewtest;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.Rect;import android.graphics.SurfaceTexture;import android.os.Bundle;import android.os.Handler;import android.os.HandlerThread;import android.os.Message;import android.support.v7.app.AppCompatActivity;import android.support.v7.widget.Toolbar;import android.view.MotionEvent;import android.view.Surface;import android.view.TextureView;import android.view.View;import java.util.ArrayList;public class MainActivity extends AppCompatActivity implements View.OnClickListener,        View.OnTouchListener, TextureView.SurfaceTextureListener{    private TextureView mSurface;    private DrawingThread mThread;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);        setSupportActionBar(toolbar);        findViewById(R.id.button_transform).setOnClickListener(this);        mSurface = (TextureView)findViewById(R.id.surface);        mSurface.setOnTouchListener(this);        mSurface.setSurfaceTextureListener(this);    }    @Override    public void onClick(View v) {        // 旋转整个绘制视图        mSurface.animate().rotation(mSurface.getRotation() < 180.f ? 180.f : 0.f);    }    @Override    public boolean onTouch(View v, MotionEvent event) {        if (event.getAction() == MotionEvent.ACTION_DOWN) {            mThread.addItem((int)event.getX(), (int)event.getY());        }        return true;    }    @Override    public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {        mThread = new DrawingThread(new Surface(surface),                 BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher));        mThread.updateSize(width, height);        mThread.start();    }    @Override    public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {        mThread.updateSize(width, height);    }    @Override    public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {        mThread.quit();        mThread = null;        // 返回 true 并允许框架释放 Surface        return true;    }    /**     *  当 SurfaceTexture 渲染一个新的帧时会调用该方法。本例中不用     */    @Override    public void onSurfaceTextureUpdated(SurfaceTexture surface) {    }    private class DrawingThread extends HandlerThread implements Handler.Callback{        private static final int MSG_ADD = 100;        private static final int MSG_MOVE = 101;        private static final int MSG_CLEAR = 102;        private int mDrawingWidth, mDrawingHeight;        private boolean mRunning = false;        private Surface mDrawingSurface;        private Rect mSurfaceRect;        private Paint mPaint;        private Handler mReceiver;        private Bitmap mIcon;        private ArrayList<DrawingItem> mLocations;        private class DrawingItem {            // 当前位置标识            int x, y;            // 运动方向的标识            boolean horizontal, vertical;            public DrawingItem(int x, int y, boolean horizontal, boolean vertical) {                this.x = x;                this.y = y;                this.horizontal = horizontal;                this.vertical = vertical;            }        }        public DrawingThread(Surface surface, Bitmap icon) {            super("DrawingThread");            mDrawingSurface = surface;            mSurfaceRect = new Rect();            mLocations = new ArrayList<>();            mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);            mIcon = icon;        }        @Override        protected void onLooperPrepared() {            mReceiver = new Handler(getLooper(), this);            // 开始渲染            mRunning = true;            mReceiver.sendEmptyMessage(MSG_MOVE);        }        @Override        public boolean quit() {            // 退出前清除所有的消息            mRunning = false;            mReceiver.removeCallbacksAndMessages(null);            return super.quit();        }        @Override        public boolean handleMessage(Message msg) {            switch (msg.what) {                case MSG_ADD:                    // 在触摸的位置创建一个新的条目，该条目的开始方向是随机的                    DrawingItem newItem = new DrawingItem(msg.arg1, msg.arg2,                            Math.round(Math.random()) == 0,                            Math.round(Math.random()) == 0);                    mLocations.add(newItem);                    break;                case MSG_CLEAR:                    // 删除所有的对象                    mLocations.clear();                    break;                case MSG_MOVE:                    // 如果取消，则不做任何事情                    if (!mRunning) return true;                    // 渲染一帧                    try {                        // 锁定 SurfaceView，并返回到要绘图的 Canvas                        Canvas canvas = mDrawingSurface.lockCanvas(mSurfaceRect);                        // 首先清空 Canvas                        canvas.drawColor(Color.BLACK);                        // 绘制每个条目                        for (DrawingItem item : mLocations) {                            // 更新位置                            item.x += (item.horizontal ? 5 : -5);                            if (item.x >= (mDrawingWidth - mIcon.getWidth())) {                                item.horizontal = false;                            }                            if (item.x <= 0) {                                item.horizontal = true;                            }                            item.y += (item.vertical ? 5 : -5);                            if (item.y >= (mDrawingHeight - mIcon.getHeight())) {                                item.vertical = false;                            }                            if (item.y <= 0) {                                item.vertical = true;                            }                            canvas.drawBitmap(mIcon, item.x, item.y, mPaint);                        }                        // 解锁 Canvas，并渲染当前的图像                        mDrawingSurface.unlockCanvasAndPost(canvas);                    } catch (Exception e) {                        e.printStackTrace();                    }                    break;            }            // 发送下一帧            if (mRunning) {                mReceiver.sendEmptyMessage(MSG_MOVE);            }            return true;        }        public void updateSize(int width, int height) {            mDrawingWidth = width;            mDrawingHeight = height;            mSurfaceRect.set(0, 0, mDrawingWidth, mDrawingHeight);        }        public void addItem(int x, int y) {            // 通过 Message 参数将位置传给处理程序            Message msg = Message.obtain(mReceiver, MSG_ADD, x, y);            mReceiver.sendMessage(msg);        }        public void clearItems() {            mReceiver.sendEmptyMessage(MSG_CLEAR);        }    }}

TextureView 提供的界面绘制 Surface 略有不同，它不通过 SurfaceHolder 封装来访问。相反，我们却可以访问一个 SurfaceTexture 实例，该实例会封装一个新的 Surface 来进行绘图。

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