本文实例为大家分享了自定义view实现了类似百度手机助手，首页评论滚动效果。

看效果：

gif做的不好，其效果就是：几个viewitem不停的向上滚动，新加入item有个淡入的效果。

说下实现思路：自定义view继承至LinearLayout，控制item数量及其动画效果，实现item复用，传入数据即可，使用方便。

代码：

/**
 * Jiantao.Yang
 *
 * @description 仿百度手机助手，评论滚动效果
 * @time 2015/1/16 17:37
 */
public class ViewFlipper extends LinearLayout {
 
 private final int MAX_SHOW_ITEM_SIZE = 5;
 
 private IAdapter mIAdapter;
 
 private int mCount;
 
 //最后一个item动画
 private Animation mLastOneAnimation;
 
 //其它item动画
 private Animation mCommonAnimation;
 
 //数据下标
 private int mCurrentIndex;
 
 /**
  * 这里动画时间是1600毫秒，所以间隔得大于动画时间
  */
 private static final int DEFAULT_INTERVAL = 2000;
 
 private int mFlipInterval = DEFAULT_INTERVAL;
 
 private boolean mAutoStart = false;
 
 private boolean mRunning = false;
 private boolean mStarted = false;
 private boolean mVisible = false;
 private boolean mUserPresent = true;
 
 public ViewFlipper(Context context) {
  super(context);
  init(context);
 }
 
 public ViewFlipper(Context context, AttributeSet attrs) {
  super(context, attrs);
  init(context);
 }
 
 public ViewFlipper(Context context, AttributeSet attrs, int defStyleAttr) {
  super(context, attrs, defStyleAttr);
  init(context);
 }
 
 private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
  @Override
  public void onReceive(Context context, Intent intent) {
   final String action = intent.getAction();
   if (Intent.ACTION_SCREEN_OFF.equals(action)) {
    mUserPresent = false;
    updateRunning();
   } else if (Intent.ACTION_USER_PRESENT.equals(action)) {
    mUserPresent = true;
    updateRunning(false);
   }
  }
 };
 
 @Override
 protected void onAttachedToWindow() {
  super.onAttachedToWindow();
 
  // Listen for broadcasts related to user-presence
  final IntentFilter filter = new IntentFilter();
  filter.addAction(Intent.ACTION_SCREEN_OFF);
  filter.addAction(Intent.ACTION_USER_PRESENT);
 
  // OK, this is gross but needed. This class is supported by the
  // remote views machanism and as a part of that the remote views
  // can be inflated by a context for another user without the app
  // having interact users permission - just for loading resources.
  // For exmaple, when adding widgets from a user profile to the
  // home screen. Therefore, we register the receiver as the current
  // user not the one the context is for.
  getContext().registerReceiver(mReceiver, filter);
 
  if (mAutoStart) {
   // Automatically start when requested
   startFlipping();
  }
 }
 
 @Override
 protected void onDetachedFromWindow() {
  super.onDetachedFromWindow();
  mVisible = false;
 
  getContext().unregisterReceiver(mReceiver);
  updateRunning();
 }
 
 @Override
 protected void onWindowVisibilityChanged(int visibility) {
  super.onWindowVisibilityChanged(visibility);
  mVisible = visibility == VISIBLE;
  updateRunning(mVisible);
//  updateRunning(false);
 }
 
 private void init(Context context) {
  this.setOrientation(LinearLayout.VERTICAL);
 }
 
 public void setIAdapter(IAdapter iAdapter) {
  this.mIAdapter = iAdapter;
  initShowItems();
 }
 
 public void startFlipping() {
  mStarted = true;
  updateRunning();
 }
 
 public void stopFlipping() {
  mStarted = false;
  updateRunning();
 }
 
 private void updateRunning() {
  updateRunning(true);
 }
 
 /**
  * Returns true if the child views are flipping.
  */
 public boolean isFlipping() {
  return mStarted;
 }
 
 /**
  * Set if this view automatically calls {@link #startFlipping()} when it
  * becomes attached to a window.
  */
 public void setAutoStart(boolean autoStart) {
  mAutoStart = autoStart;
 }
 
 /**
  * Returns true if this view automatically calls {@link #startFlipping()}
  * when it becomes attached to a window.
  */
 public boolean isAutoStart() {
  return mAutoStart;
 }
 
 @Override
 public void onInitializeAccessibilityEvent(AccessibilityEvent event) {
  super.onInitializeAccessibilityEvent(event);
  event.setClassName(ViewFlipper.class.getName());
 }
 
 @Override
 public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) {
  super.onInitializeAccessibilityNodeInfo(info);
  info.setClassName(ViewFlipper.class.getName());
 }
 
 /**
  * 初始化childViews
  */
 private void initShowItems() {
  if (mIAdapter != null) {
   mCount = mIAdapter.getCount();
   for (int i = 0; i < mCount; i++) {
    if (i == MAX_SHOW_ITEM_SIZE) {
     break;
    }
    View convertView = getChildAt(i);
    View item = mIAdapter.getItemView(convertView, i);
    addView(item, i);
   }
  }
 }
 
 /**
  * Internal method to start or stop dispatching flip {@link android.os.Message} based
  * on {@link #mRunning} and {@link #mVisible} state.
  *
  * @param flipNow Determines whether or not to execute the animation now, in
  *    addition to queuing future flips. If omitted, defaults to
  *    true.
  */
 private void updateRunning(boolean flipNow) {
  boolean running = mVisible && mStarted && mUserPresent;
  System.out.println(" updateRunning running:" + running + " mVisible " + mVisible + " userPresent " + mUserPresent);
  if (running != mRunning) {
   if (running && (mCount > MAX_SHOW_ITEM_SIZE)) {
    showItems(mCurrentIndex++, flipNow);
    Message msg = mHandler.obtainMessage(FLIP_MSG);
    mHandler.sendMessageDelayed(msg, mFlipInterval);
   } else {
    mHandler.removeMessages(FLIP_MSG);
   }
   mRunning = running;
  }
 }
 
 
 private void showItems(final int position, boolean animate) {
  if (animate && (mLastOneAnimation == null || mCommonAnimation == null)) {
   mLastOneAnimation = AnimationUtils.loadAnimation(getContext(), R.anim.lastone_anim);
   mCommonAnimation = AnimationUtils.loadAnimation(getContext(), R.anim.common_anim);
  }
  int childCount = getChildCount();
  for (int i = 0; i < childCount; i++) {
   View child = getChildAt(i);
   child.clearAnimation();
   int index = position + i;
   child = mIAdapter.getItemView(child, (index >= mIAdapter.getCount()) ? (index - mIAdapter.getCount()) : index);
   if (animate) {
    if (i == childCount - 1) {
     child.setAnimation(mLastOneAnimation);
    } else {
     child.setAnimation(mCommonAnimation);
    }
   }
   child.setVisibility(View.VISIBLE);
  }
  if (animate) {
   mCommonAnimation.startNow();
   mLastOneAnimation.startNow();
  }
 
  //保证传入的position小于getCount
  if (mCurrentIndex >= mIAdapter.getCount()) {
   mCurrentIndex = 0;
  }
 }
 
 private final int FLIP_MSG = 1;
 
 private final Handler mHandler = new Handler() {
  @Override
  public void handleMessage(Message msg) {
   if (msg.what == FLIP_MSG) {
    if (mRunning) {
     showItems(mCurrentIndex++, true);
     msg = obtainMessage(FLIP_MSG);
     sendMessageDelayed(msg, mFlipInterval);
    }
   }
  }
 };
 
 public interface IAdapter {
 
  /**
   * @param convertView
   * @param position
   * @return
   */
  public View getItemView(View convertView, int position);
 
  /**
   * @return 数据count
   */
  public int getCount();
 
 }
 
}

再来看看调用部分：

public class MainActivity extends ActionBarActivity implements ViewFlipper.IAdapter {
 
 ViewFlipper viewFlipper;
 
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  viewFlipper = (ViewFlipper) findViewById(R.id.view_flipper);
  viewFlipper.setIAdapter(this);
 }
 
 @Override
 protected void onResume() {
  super.onResume();
  viewFlipper.startFlipping();
 }
 
 @Override
 public View getItemView(View convertView, int position) {
  View item = null;
  TextView textView;
  if (convertView == null) {
   item = View.inflate(this, R.layout.item, null);
  } else {
   item = convertView;
  }
  textView = (TextView) item.findViewById(R.id.textview);
  textView.setText("测试数据:" + position);
  return item;
 }
 
 @Override
 public int getCount() {
  return 8;
 }
}

可以看出，MainActivity实现了ViewFlipper.IAdapter接口，setAdapter后调用startFlipper即可。

这里布局文件我就不贴出来了，附上工程源码，项目里动画时间有点长，修改下就ok。

限于水平有限，不足之处难免，望各位不舍指正，与君共勉。

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持海外IDC网。