在Android中显示GIF动画

Posted 2022-08-12 非著名程序员

gif图动画在android中还是比较常用的，比如像新浪微博中，有很多gif图片，而且展示非常好，所以我也想弄一个。经过我多方的搜索资料和整理，终于弄出来了，其实github上有很多开源的gif的展示代码，我下载过几个，但是都不是很理想，不是我完全想要的。所以有时候就得自己学会总结，把开源的东西整理成自己的，现在无聊，也正好有朋友需要，所以现在整理了一下，留着以后备用！

废话不多说，直接上图：

在这里主要用的是：android中的android.graphics.Movie 这个类，这是android提供给我们的一个非常方便的工具。

首先，重写控件View,自定义一个展示gif图的GifView，代码如下：

package net.loonggg.gif.view;

import net.loonggg.gif.R;
import android.annotation.SuppressLint;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Movie;
import android.os.Build;
import android.util.AttributeSet;
import android.view.View;

public class GifView extends View 

	/**
	 * 默认为1秒
	 */
	private static final int DEFAULT_MOVIE_DURATION = 1000;

	private int mMovieResourceId;

	private Movie mMovie;

	private long mMovieStart;

	private int mCurrentAnimationTime = 0;

	private float mLeft;

	private float mTop;

	private float mScale;

	private int mMeasuredMovieWidth;

	private int mMeasuredMovieHeight;

	private boolean mVisible = true;

	private volatile boolean mPaused = false;

	public GifView(Context context) 
		this(context, null);
	

	public GifView(Context context, AttributeSet attrs) 
		this(context, attrs, R.styleable.CustomTheme_gifViewStyle);
	

	public GifView(Context context, AttributeSet attrs, int defStyle) 
		super(context, attrs, defStyle);
		setViewAttributes(context, attrs, defStyle);
	

	@SuppressLint("NewApi")
	private void setViewAttributes(Context context, AttributeSet attrs,
			int defStyle) 
		if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) 
			setLayerType(View.LAYER_TYPE_SOFTWARE, null);
		
		// 从描述文件中读出gif的值，创建出Movie实例
		final TypedArray array = context.obtainStyledAttributes(attrs,
				R.styleable.GifView, defStyle, R.style.Widget_GifView);
		mMovieResourceId = array.getResourceId(R.styleable.GifView_gif, -1);
		mPaused = array.getBoolean(R.styleable.GifView_paused, false);
		array.recycle();
		if (mMovieResourceId != -1) 
			mMovie = Movie.decodeStream(getResources().openRawResource(
					mMovieResourceId));
		
	

	/**
	 * 设置gif图资源
	 * 
	 * @param movieResId
	 */
	public void setMovieResource(int movieResId) 
		this.mMovieResourceId = movieResId;
		mMovie = Movie.decodeStream(getResources().openRawResource(
				mMovieResourceId));
		requestLayout();
	

	public void setMovie(Movie movie) 
		this.mMovie = movie;
		requestLayout();
	

	public Movie getMovie() 
		return mMovie;
	

	public void setMovieTime(int time) 
		mCurrentAnimationTime = time;
		invalidate();
	

	/**
	 * 设置暂停
	 * 
	 * @param paused
	 */
	public void setPaused(boolean paused) 
		this.mPaused = paused;
		if (!paused) 
			mMovieStart = android.os.SystemClock.uptimeMillis()
					- mCurrentAnimationTime;
		
		invalidate();
	

	/**
	 * 判断gif图是否停止了
	 * 
	 * @return
	 */
	public boolean isPaused() 
		return this.mPaused;
	

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) 
		if (mMovie != null) 
			int movieWidth = mMovie.width();
			int movieHeight = mMovie.height();
			int maximumWidth = MeasureSpec.getSize(widthMeasureSpec);
			float scaleW = (float) movieWidth / (float) maximumWidth;
			mScale = 1f / scaleW;
			mMeasuredMovieWidth = maximumWidth;
			mMeasuredMovieHeight = (int) (movieHeight * mScale);
			setMeasuredDimension(mMeasuredMovieWidth, mMeasuredMovieHeight);
		 else 
			setMeasuredDimension(getSuggestedMinimumWidth(),
					getSuggestedMinimumHeight());
		
	

	@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b) 
		super.onLayout(changed, l, t, r, b);
		mLeft = (getWidth() - mMeasuredMovieWidth) / 2f;
		mTop = (getHeight() - mMeasuredMovieHeight) / 2f;
		mVisible = getVisibility() == View.VISIBLE;
	

	@Override
	protected void onDraw(Canvas canvas) 
		if (mMovie != null) 
			if (!mPaused) 
				updateAnimationTime();
				drawMovieFrame(canvas);
				invalidateView();
			 else 
				drawMovieFrame(canvas);
			
		
	

	@SuppressLint("NewApi")
	private void invalidateView() 
		if (mVisible) 
			if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) 
				postInvalidateOnAnimation();
			 else 
				invalidate();
			
		
	

	private void updateAnimationTime() 
		long now = android.os.SystemClock.uptimeMillis();
		// 如果第一帧，记录起始时间
		if (mMovieStart == 0) 
			mMovieStart = now;
		
		// 取出动画的时长
		int dur = mMovie.duration();
		if (dur == 0) 
			dur = DEFAULT_MOVIE_DURATION;
		
		// 算出需要显示第几帧
		mCurrentAnimationTime = (int) ((now - mMovieStart) % dur);
	

	private void drawMovieFrame(Canvas canvas) 
		// 设置要显示的帧，绘制即可
		mMovie.setTime(mCurrentAnimationTime);
		canvas.save(Canvas.MATRIX_SAVE_FLAG);
		canvas.scale(mScale, mScale);
		mMovie.draw(canvas, mLeft / mScale, mTop / mScale);
		canvas.restore();
	

	@SuppressLint("NewApi")
	@Override
	public void onScreenStateChanged(int screenState) 
		super.onScreenStateChanged(screenState);
		mVisible = screenState == SCREEN_STATE_ON;
		invalidateView();
	

	@SuppressLint("NewApi")
	@Override
	protected void onVisibilityChanged(View changedView, int visibility) 
		super.onVisibilityChanged(changedView, visibility);
		mVisible = visibility == View.VISIBLE;
		invalidateView();
	

	@Override
	protected void onWindowVisibilityChanged(int visibility) 
		super.onWindowVisibilityChanged(visibility);
		mVisible = visibility == View.VISIBLE;
		invalidateView();
	

Movie其实管理着GIF动画中的多个帧，只需要通过 setTime() 一下就可以让它在draw()的时候绘出相应的那帧图像。通过当前时间与duration之间的换算关系，是很容易实现GIF动起来的效果。

其次，在xml布局文件中，把这个view定义进去，代码如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <net.loonggg.gif.view.GifView
        android:id="@+id/gif1"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_gravity="center_horizontal"
        android:enabled="false" />

    <net.loonggg.gif.view.GifView
        android:id="@+id/gif2"
        android:layout_width="200dp"
        android:layout_height="200dp"
        android:layout_gravity="center_horizontal"
        android:enabled="false" />

</LinearLayout>

最后，在MainActivity中的使用，代码如下：

package net.loonggg.gif;

import net.loonggg.gif.view.GifView;
import android.app.Activity;
import android.os.Bundle;

public class Gif extends Activity 
	private GifView gif1, gif2;

	@Override
	public void onCreate(Bundle savedInstanceState) 
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		gif1 = (GifView) findViewById(R.id.gif1);
		// 设置背景gif图片资源
		gif1.setMovieResource(R.raw.kitty);
		gif2 = (GifView) findViewById(R.id.gif2);
		gif2.setMovieResource(R.raw.b);
		// 设置暂停
		// gif2.setPaused(true);

	

注意：与ImageView和其他View唯一的区别在于我加了一个gif属性。

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <declare-styleable name="GifView">
        <attr name="gif" format="reference" />
        <attr name="paused" format="boolean" />
    </declare-styleable>
    <declare-styleable name="CustomTheme">
        <attr name="gifViewStyle" format="reference" />
    </declare-styleable>

</resources>

这个代码已经非常好了，使用也非常方便，其实不懂代码是什么意思也可以很好的用，只需要懂得我写注释的那几行和Activity里面的那几行代码就可以了！

转载请注明出处：http://blog.csdn.net/loongggdroid/article/details/21166563

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