Android 弹幕效果开发案例

一、概述

现在有个很流行的效果就是弹幕效果，满屏幕的文字从右到左飘来飘去。看的眼花缭乱，看起来还蛮cool的

现在就是来实现这一的一个效果，大部分的都是从右向左移动漂移，本文的效果中也支持从左向右的漂移移动

效果，同时也支持屏幕弹幕最多显示个数的设置。

二、效果图

废话不说，先来看看效果图吧~~

三、实现原理方案

1、自定义ViewGroup-XCDanmuView，继承RelativeLayout来实现，当然也可以继承其他三大布局类哈

2、初始化若干个TextView（弹幕的item View，这里以TextView 为例，当然也可以其他了~），然后通过addView添加到自定义View中

3、通过addView添加到XCDanmuView中，位置在坐标，为了实现 从屏幕外移动进来的效果

我们还需要修改添加进来TextView的位置，以从右向左移动方向来说，addView后必须将该TextView的位置设置到右边的屏幕外

这样我们采用的方法，是在onLayout（）方法中对childView进行layout重新布局设置位置

4、随机冲左侧或右侧出来弹幕itemView，移动采用属性动画来实现平移，从屏幕的一端移动到另一端，当动画结束后，就将

该child从XCDanmuView中remove掉。并重新new 一个弹幕itemView ，并addView到XCDanmuView中，并开始动画移动

5、本自定义弹幕View支持从左到右和从右到左两个方向，支持自定义设置屏幕弹幕最多显示个数。

四、自定义弹幕效果XCDanmuView的具体实现

1、初始化需要用到的数据变量

private int mWidth; private int mScreenWidth; private List<View> mChildList; private boolean mIsWorking = false; private Context mContext; private int mMaxShowNum = 15; private int mRowNum = 4; private int[] mSpeeds = { 3000,4000,5000,6000
}; private int mDelayDuration = 500; private int[] mBgResIds = {
R.drawable.bg_danmu0,
R.drawable.bg_danmu1,
R.drawable.bg_danmu2,
R.drawable.bg_danmu3
}; private int[] mRowPos = { 150,140,160,150
}; private Random mRandom; private String[] mStrContents; public static enum XCDirection{
FROM_RIGHT_TO_LEFT,
FORM_LEFT_TO_RIGHT
} public enum XCAction{
SHOW,HIDE
} private XCDirection mDirection = XCDirection.FROM_RIGHT_TO_LEFT;

private void init() {
mScreenWidth = getScreenWidth();
mChildList = new ArrayList<>();
mRandom = new Random();
}

2、初始化若干个弹幕item view

public void initDanmuItemViews(String[] strContents){
mStrContents = strContents; for(int i = 0; i < mMaxShowNum; i ++){ int index = mRandom.nextInt(100) % strContents.length;
createDanmuView(i,strContents[index],false);
}
}

3、创建弹幕item view 并addView到XCDanmuView中

public void createDanmuView(int index,String content,boolean reset){ final TextView textView = new TextView(mContext);
textView.setTextColor(Color.WHITE); int r = mRandom.nextInt(100) % mRowNum;
textView.setBackgroundResource(mBgResIds[r]);
textView.setText(content +"_"+ (index+1));
RelativeLayout.LayoutParams lp = new LayoutParams(LayoutParams.WRAP_CONTENT,
RelativeLayout.LayoutParams.WRAP_CONTENT); int row = mRandom.nextInt(100) % mRowNum; while(row == lastRow){
row = mRandom.nextInt(100)% mRowNum;
} int pos = mRandom.nextInt(100)% mRowNum;
lp.topMargin = row * mRowPos[pos];
lastRow = row;
textView.setLayoutParams(lp);
textView.setPadding(40, 2, 40, 2); this.addView(textView); if(reset){
mChildList.set(index,textView);
}else{
mChildList.add(index,textView);
}
textView.setClickable(true);
textView.setOnClickListener(new OnClickListener() {
@Override public void onClick(View view) {
Toast toast = Toast.makeText(mContext, textView.getText(), Toast.LENGTH_SHORT);
toast.setGravity(Gravity.TOP,0,50);
toast.show();
}
});
}

4、重新设置childView的初始位置到屏幕之外

@Override protected void onLayout(boolean changed, int l, int t, int r, int b) { super.onLayout(changed, l, t, r, b); int childCount = this.getChildCount(); for(int i=0;i<childCount;i++){
View view = getChildAt(i);
RelativeLayout.LayoutParams lp = (LayoutParams) view.getLayoutParams(); if(lp.leftMargin <= 0){ if(mDirection == XCDirection.FORM_LEFT_TO_RIGHT){
view.layout(-view.getMeasuredWidth(), lp.topMargin, 0,lp.topMargin + view.getMeasuredHeight());
}else{
view.layout(mScreenWidth,lp.topMargin,mScreenWidth+view.getMeasuredWidth(),
lp.topMargin+view.getMeasuredHeight());
} }else{ continue;
}
}
}

5、弹幕item view的移动效果

private Handler mHandler = new Handler() {
@Override public void handleMessage(final Message msg) { super.handleMessage(msg); final int pos = msg.what;
ViewPropertyAnimator animator; if(mDirection == XCDirection.FROM_RIGHT_TO_LEFT){
animator = mChildList.get(msg.what).animate()
.translationXBy(-(mScreenWidth + mChildList.get(msg.what).getWidth()));
}else{
animator = mChildList.get(msg.what).animate()
.translationXBy(mScreenWidth + mChildList.get(msg.what).getWidth());
} Random random = new Random(System.currentTimeMillis()); int index = random.nextInt(100) % mSpeeds.length;
animator.setDuration(mSpeeds[index]);
animator.setInterpolator(new LinearInterpolator());
animator.setListener(new Animator.AnimatorListener() {
@Override public void onAnimationStart(Animator animator) { } @Override public void onAnimationEnd(Animator animator) {
XCDanmuView.this.removeView(mChildList.get(pos)); int index = mRandom.nextInt(100) % mStrContents.length;
createDanmuView(pos, mStrContents[index], true);
mHandler.sendEmptyMessageDelayed(pos, mDelayDuration);
Log.v("czm", "size=" + mChildList.size());
} @Override public void onAnimationCancel(Animator animator) { } @Override public void onAnimationRepeat(Animator animator) { }
});
animator.start();
}
};

6、开启弹幕效果和关闭弹幕效果以及对于的动画效果

boolean isFirst = true; public void start(){
switchAnimation(XCAction.SHOW); if(isFirst){ for(int i =0;i< mChildList.size();i++){
mHandler.sendEmptyMessageDelayed(i,i * mDelayDuration);
}
isFirst = false;
} mIsWorking = true;
} public void hide(){
switchAnimation(XCAction.HIDE);
mIsWorking =false;
} public void stop(){ this.setVisibility(View.GONE); for(int i =0;i< mChildList.size();i++){
mChildList.get(i).clearAnimation();
mHandler.removeMessages(i);
}
mIsWorking =false;
}private void switchAnimation(final XCAction action){
AlphaAnimation animation; if(action == XCAction.HIDE){
animation = new AlphaAnimation(1.0f,0.0f);
animation.setDuration(400);
}else{
animation = new AlphaAnimation(0.0f,1.0f);
animation.setDuration(1000);
}
XCDanmuView.this.startAnimation(animation);
animation.setAnimationListener(new Animation.AnimationListener() {
@Override public void onAnimationStart(Animation animation) { }
@Override public void onAnimationEnd(Animation animation) { if(action == XCAction.HIDE){
XCDanmuView.this.setVisibility(View.GONE);
}else{
XCDanmuView.this.setVisibility(View.VISIBLE);
}
}
@Override public void onAnimationRepeat(Animation animation) { }
});
}

五、如何使用该自定义侧滑View控件

使用该自定义View非常简单，控件默认效果从右向左，如果需要修改方向为从左到右，只需设置下方向即可

public class MainActivity extends Activity { private XCDanmuView mDanmuView; private List<View> mViewList; private String[] mStrItems = { "搜狗","百度", "腾讯","360", "阿里巴巴","搜狐", "网易","新浪", "搜狗-上网从搜狗开始","百度一下,你就知道", "必应搜索-有求必应","好搜-用好搜，特顺手", "Android-谷歌","IOS-苹果", "Windows-微软","Linux"
};
@Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initDanmuView();
initListener();
} private void initListener() {
findViewById(R.id.btn).setOnClickListener(new View.OnClickListener() {
@Override public void onClick(View view) { if (mDanmuView.isWorking()) {
mDanmuView.hide();
((Button) view).setText("开启弹幕");
} else {
mDanmuView.start();
((Button) view).setText("关闭弹幕");
}
}
});
} private void initDanmuView() {
mDanmuView = (XCDanmuView)findViewById(R.id.danmu);
mDanmuView.initDanmuItemViews(mStrItems);
}}

六、项目程序结构目录截图