安卓类画廊滑动放大功能实现。

今天因为一个项目需求一个滑动放大功能学习了这个功能。

这个是我的实现截图

学习文章地址：https://blog.csdn.net/vipdatoucth/article/details/64128290

我先做个概述：通过确定每个item与边界的距离来确定每个item的放大尺寸。

通过给RecycleView设置滚动监听，在 onScrolled 中完成功能。

    具体的算法是：

1.规定缩放比例的最大值和最小值 MAX_SCALE(eg: 1.2f) 和 MIN_SCALE(eg:0.85f)

2.当滑动的时候，计算recycleview的所有可用的子view的左边界(left = View.getLeft())和右边界(left = View.getRight())的距离比例 percent = left <0|| right <0?0: Math.min(left, right) *1f/ Math.max(left, right);

3.计算每个子view的缩放比例：floatscaleFactor =MIN_SCALE+ Math.abs(percent) * (MAX_SCALE-MIN_SCALE);

child.setScaleY(scaleFactor);

public class MainActivity extends AppCompatActivity {
    private List<icon> list = new ArrayList<>();
    private int mScreenWidth;
    private static final float MIN_SCALE = .95f;
    private static final float MAX_SCALE = 1.15f;
    private LinearLayoutManager mLinearLayoutManager;
    private int mMinWidth;
    private int mMaxWidth;
    RecyclerView recyclerView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //设置布局充满全屏
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN);

        initIcon();
        mScreenWidth = getResources().getDisplayMetrics().widthPixels;
        mMinWidth = (int) (mScreenWidth * 0.28f);
        mMaxWidth = mScreenWidth - 2 * mMinWidth;
        recyclerView = (RecyclerView) findViewById(R.id.icon_name_item);
        mLinearLayoutManager = new LinearLayoutManager(this);
        mLinearLayoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
        new LinearSnapHelper().attachToRecyclerView(recyclerView);
        recyclerView.setLayoutManager(mLinearLayoutManager);
        iconAdapter adapter = new iconAdapter(list);
        recyclerView.setAdapter(adapter);
        recyclerView.addOnScrollListener(mOnScrollListener);//设置监听器
    }

    private RecyclerView.OnScrollListener mOnScrollListener = new RecyclerView.OnScrollListener() {//监听器方法
        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            final int childCount = recyclerView.getChildCount();//获取可见item数量
           // Log.e("tag", childCount + "");
            for (int i = 0; i < childCount; i++) {
                LinearLayout child = (LinearLayout) recyclerView.getChildAt(i);
                RecyclerView.LayoutParams lp = (RecyclerView.LayoutParams) child.getLayoutParams();
                lp.rightMargin = 3;
                lp.height=500;


                int left = child.getLeft();
                int right = mScreenWidth - child.getRight();
                final float percent = left < 0 || right < 0 ? 0 : Math.min(left, right) * 1f / Math.max(left, right);
               // Log.e("tag", "percent = " + percent);
                float scaleFactor = MIN_SCALE + Math.abs(percent) * (MAX_SCALE - MIN_SCALE);//放大算法
               // int width = (int) (mMinWidth + Math.abs(percent) * (mMaxWidth - mMinWidth));
                lp.width = 500;

                child.setLayoutParams(lp);
                child.setScaleY(scaleFactor);//将高度放大
                child.setScaleX(scaleFactor);//将宽度放大
                if (percent > 1f / 5) {
                    ((TextView) child.getChildAt(1)).setTextColor(Color.BLUE);
                } else {
                    ((TextView) child.getChildAt(1)).setTextColor(Color.BLACK);
                }
            }
        }
    };
    private void initIcon() {//初始化
for (int i=0;i<10;i++){
            icon qq = new icon("qq", R.drawable.qq);
            list.add(qq);
            icon wechat = new icon("wechat", R.drawable.wechat);
            list.add(wechat);

    }}
}

主活动布局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical"
    tools:context="com.example.thinkpad.adas.MainActivity">
    <TextClock
        android:id="@+id/textClock"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:format24Hour="HH:mm"
        android:textSize="100sp"
        android:textStyle="bold"
        android:background="@color/colorDark"
        />
    <View
        android:layout_width="match_parent"
        android:layout_height="5dp"
        android:background="#000"
        />

        <android.support.v7.widget.RecyclerView
            android:id="@+id/icon_name_item"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerVertical="true"
            android:background="@color/colorDark"
            android:clipChildren="false"         />

</LinearLayout>

recyclerview子项布局

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

    android:layout_gravity="center"
    >


        <ImageButton
            android:background="@drawable/mainbt_selector"
            android:layout_marginTop="30dp"
            android:id="@+id/icon_image"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"

            />
        <TextView
            android:id="@+id/icon_name"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:textSize="24sp"
            android:gravity="center"
            android:layout_marginLeft="10dp"/>


</LinearLayout>