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详解Android使用CoordinatorLayout+AppBarLayout实现拉伸顶部图片功能

一、国际惯例，先看下效果图

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详解Android使用CoordinatorLayout+AppBarLayout实现拉伸顶部图片功能

二、不跟你多bb直接上布局文件代码

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

三、上java代码

package com.ce.myscrollimg;
import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;
import androidx.viewpager.widget.ViewPager;
import android.graphics.Typeface;
import android.os.Bundle;
import android.util.TypedValue;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.TextView;
import com.google.android.material.tabs.TabLayout;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
 private TabLayout toolbar_tab;
 private NoScrollViewPager vp_content;
 private ViewPagerAdapter vpAdapter;
 private List listFragment = new ArrayList<>();
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  initView();
 }
 //初始化view
 private void initView(){
  //tab
  toolbar_tab = findViewById(R.id.toolbar_tab);
  //
  vp_content = findViewById(R.id.vp_content);
  vpAdapter = new ViewPagerAdapter(getSupportFragmentManager(),listFragment);
  vp_content.setAdapter(vpAdapter);
  vp_content.setOffscreenPageLimit(2);
  toolbar_tab.setupWithViewPager(vp_content);
  for(int i=0;i<12;i++){
   listFragment.add(CeshiFragment.newInstance("第"+i+"页"));
  }
  vpAdapter.notifyDataSetChanged();
  for(int i=0;i

四、重点在于设置AppBarLayout的Behavior这里自定义AppBarLayoutOverScrollViewBehavior，下面贴出代码

package com.ce.myscrollimg;
import android.animation.Animator;
import android.animation.ValueAnimator;
import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import androidx.appcompat.widget.Toolbar;
import androidx.coordinatorlayout.widget.CoordinatorLayout;
import androidx.core.view.ViewCompat;
import com.google.android.material.appbar.AppBarLayout;
/**
 * Created by gjm on 2017/5/24.
 * 目前包括的事件：
 * 图片放大回弹
 * 个人信息布局的top和botoom跟随图片位移
 * toolbar背景变色
 */
public class AppBarLayoutOverScrollViewBehavior extends AppBarLayout.Behavior {
 private static final String TAG = "overScroll";
 private static final String TAG_TOOLBAR = "toolbar";
 private static final String TAG_MIDDLE = "middle";
 private static final float TARGET_HEIGHT = 1500;
 private View mTargetView;
 private int mParentHeight;
 private int mTargetViewHeight;
 private float mTotalDy;
 private float mLastScale;
 private int mLastBottom;
 private boolean isAnimate;
 private Toolbar mToolBar;
 private ViewGroup middleLayout;//个人信息布局
 private int mMiddleHeight;
 private boolean isRecovering = false;//是否正在自动回弹中
 private final float MAX_REFRESH_LIMIT = 0.3f;//达到这个下拉临界值就开始刷新动画
 public AppBarLayoutOverScrollViewBehavior() {
 }
 public AppBarLayoutOverScrollViewBehavior(Context context, AttributeSet attrs) {
  super(context, attrs);
 }
 @Override
 public boolean onLayoutChild(CoordinatorLayout parent, AppBarLayout abl, int layoutDirection) {
  boolean handled = super.onLayoutChild(parent, abl, layoutDirection);
  if (mToolBar == null) {
   mToolBar = parent.findViewWithTag(TAG_TOOLBAR);
  }
  if (middleLayout == null) {
   middleLayout = (ViewGroup) parent.findViewWithTag(TAG_MIDDLE);
  }
  // 需要在调用过super.onLayoutChild()方法之后获取
  if (mTargetView == null) {
   mTargetView = parent.findViewById(R.id.iv_bg);
   if (mTargetView != null) {
    initial(abl);
   }
  }
  abl.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
   @Override
   public final void onOffsetChanged(AppBarLayout appBarLayout, int i) {
    mToolBar.setAlpha(Float.valueOf(Math.abs(i)) / Float.valueOf(appBarLayout.getTotalScrollRange()));
   }
  });
  return handled;
 }
 @Override
 public boolean onStartNestedScroll(CoordinatorLayout parent, AppBarLayout child, View directTargetChild, View target, int nestedScrollAxes, int x) {
  isAnimate = true;
  if (target instanceof DisInterceptNestedScrollView) return true;//这个布局就是middleLayout
  return super.onStartNestedScroll(parent, child, directTargetChild, target, nestedScrollAxes,x);
 }
 @Override
 public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, int dx, int dy, int[] consumed, int x) {
  if (!isRecovering) {
   if (mTargetView != null && ((dy < 0 && child.getBottom() >= mParentHeight)
     || (dy > 0 && child.getBottom() > mParentHeight))) {
    scale(child, target, dy);
    return;
   }
  }
  super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed,x);
 }
 @Override
 public boolean onNestedPreFling(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, float velocityX, float velocityY) {
  if (velocityY > 100) {//当y速度>100,就秒弹回
   isAnimate = false;
  }
  return super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY);
 }
 @Override
 public void onStopNestedScroll(CoordinatorLayout coordinatorLayout, AppBarLayout abl, View target, int x) {
  recovery(abl);
  super.onStopNestedScroll(coordinatorLayout, abl, target,x);
 }
 private void initial(AppBarLayout abl) {
  abl.setClipChildren(false);
  mParentHeight = abl.getHeight();
  mTargetViewHeight = mTargetView.getHeight();
  mMiddleHeight = middleLayout.getHeight();
 }
 private void scale(AppBarLayout abl, View target, int dy) {
  mTotalDy += -dy;
  mTotalDy = Math.min(mTotalDy, TARGET_HEIGHT);
  mLastScale = Math.max(1f, 1f + mTotalDy / TARGET_HEIGHT);
  ViewCompat.setScaleX(mTargetView, mLastScale);
  ViewCompat.setScaleY(mTargetView, mLastScale);
  mLastBottom = mParentHeight + (int) (mTargetViewHeight / 2 * (mLastScale - 1));
  abl.setBottom(mLastBottom);
  target.setScrollY(0);
  middleLayout.setTop(mLastBottom - mMiddleHeight);
  middleLayout.setBottom(mLastBottom);
  if (onProgressChangeListener != null) {
   float progress = Math.min((mLastScale - 1) / MAX_REFRESH_LIMIT, 1);//计算0~1的进度
   onProgressChangeListener.onProgressChange(progress, false);
  }
 }
 public interface onProgressChangeListener {
  /**
   * 范围 0~1
   *
   * @param progress
   * @param isRelease 是否是释放状态
   */
  void onProgressChange(float progress, boolean isRelease);
 }
 public void setOnProgressChangeListener(AppBarLayoutOverScrollViewBehavior.onProgressChangeListener onProgressChangeListener) {
  this.onProgressChangeListener = onProgressChangeListener;
 }
 onProgressChangeListener onProgressChangeListener;
 private void recovery(final AppBarLayout abl) {
  if (isRecovering) return;
  if (mTotalDy > 0) {
   isRecovering = true;
   mTotalDy = 0;
   if (isAnimate) {
    ValueAnimator anim = ValueAnimator.ofFloat(mLastScale, 1f).setDuration(200);
    anim.addUpdateListener(
      new ValueAnimator.AnimatorUpdateListener() {
       @Override
       public void onAnimationUpdate(ValueAnimator animation) {
        float value = (float) animation.getAnimatedValue();
        ViewCompat.setScaleX(mTargetView, value);
        ViewCompat.setScaleY(mTargetView, value);
        abl.setBottom((int) (mLastBottom - (mLastBottom - mParentHeight) * animation.getAnimatedFraction()));
        middleLayout.setTop((int) (mLastBottom -
          (mLastBottom - mParentHeight) * animation.getAnimatedFraction() - mMiddleHeight));
        if (onProgressChangeListener != null) {
         float progress = Math.min((value - 1) / MAX_REFRESH_LIMIT, 1);//计算0~1的进度
         onProgressChangeListener.onProgressChange(progress, true);
        }
       }
      }
    );
    anim.addListener(new Animator.AnimatorListener() {
     @Override
     public void onAnimationStart(Animator animation) {
     }
     @Override
     public void onAnimationEnd(Animator animation) {
      isRecovering = false;
     }
     @Override
     public void onAnimationCancel(Animator animation) {
     }
     @Override
     public void onAnimationRepeat(Animator animation) {
     }
    });
    anim.start();
   } else {
    ViewCompat.setScaleX(mTargetView, 1f);
    ViewCompat.setScaleY(mTargetView, 1f);
    abl.setBottom(mParentHeight);
    middleLayout.setTop(mParentHeight - mMiddleHeight);
//    middleLayout.setBottom(mParentHeight);
    isRecovering = false;
    if (onProgressChangeListener != null)
     onProgressChangeListener.onProgressChange(0, true);
   }
  }
 }
}

五、源码下载

http://xiazai.jb51.net/201910/yuanma/MyScrollImg_jb51.rar

总结

以上所述是小编给大家介绍的Android使用CoordinatorLayout+AppBarLayout实现拉伸顶部图片功能,希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对创新互联网站的支持！
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