android implement RecyclerView pinch to zoom by ScaleGestureDetector and GridLayoutManager ，java（1）

小鱼儿 2023-09-24 21:31 95阅读 0赞

## android implement RecyclerView pinch to zoom by ScaleGestureDetector and GridLayoutManager ，java（1） ##

a simple implements , use ScaleGestureDetector and GridLayoutManager.

MainActivy：

import androidx.annotation.NonNull;
    import androidx.appcompat.app.AppCompatActivity;
    import androidx.recyclerview.widget.GridLayoutManager;
    import androidx.recyclerview.widget.RecyclerView;
    
    import android.os.Bundle;
    import android.util.Log;
    import android.view.MotionEvent;
    import android.view.ScaleGestureDetector;
    import android.view.View;
    
    public class MainActivity extends AppCompatActivity {
        private RecyclerView mRecyclerView;
    
        private PhotoAdapter mPhotoAdapter;
    
        private GridLayoutManager mLayoutManager;
    
        private ScaleGestureDetector mScaleGestureDetector;
    
        private String TAG = "ZHANGPHIL";
    
        private final int[] ZOOM = {1, 2, 3, 4, 6, 8, 10, 15, 20};
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            mRecyclerView = findViewById(R.id.recycler_view);
    
            mLayoutManager = new GridLayoutManager(this, ZOOM[2]);
            mLayoutManager.setOrientation(GridLayoutManager.VERTICAL);
            mRecyclerView.setLayoutManager(mLayoutManager);
    
            mScaleGestureDetector = new ScaleGestureDetector(this, new ScaleGestureDetector.SimpleOnScaleGestureListener() {
                @Override
                public boolean onScaleBegin(@NonNull ScaleGestureDetector detector) {
                    return super.onScaleBegin(detector);
                }
    
                @Override
                public boolean onScale(ScaleGestureDetector detector) {
                    return super.onScale(detector);
                }
    
                @Override
                public void onScaleEnd(ScaleGestureDetector detector) {
                    super.onScaleEnd(detector);
    
                    Log.d(TAG, "----------");
                    Log.d(TAG, "onScaleEnd");
                    Log.d(TAG, "TimeDelta-" + detector.getTimeDelta());
                    Log.d(TAG, "ScaleFactor-" + detector.getScaleFactor());
    
                    scale(detector);
                }
    
                private boolean scale(ScaleGestureDetector detector) {
                    if (detector.getCurrentSpan() > 20 && detector.getTimeDelta() > 50) {
                        float scaleFactor = detector.getScaleFactor();
                        int curSpanCount = mLayoutManager.getSpanCount();
                        Log.d(TAG, "LayoutManager SpanCount()-" + curSpanCount);
                        int curIndex = getSpanCountIndex(curSpanCount);
                        if (scaleFactor < 1) {
                            if (curSpanCount == ZOOM[ZOOM.length - 1]) {
                                return true;
                            } else {
                                mLayoutManager.setSpanCount(ZOOM[curIndex + 1]);
                            }
                        } else {
                            if (curSpanCount == ZOOM[0]) {
                                return true;
                            } else {
                                mLayoutManager.setSpanCount(ZOOM[curIndex - 1]);
                            }
                        }
    
                        mRecyclerView.setLayoutManager(mLayoutManager);
                        mPhotoAdapter.dataSetChanged();
    
                        return true;
                    }
    
                    return false;
                }
            });
    
    
            mRecyclerView.setOnTouchListener(new View.OnTouchListener() {
                @Override
                public boolean onTouch(View v, MotionEvent event) {
                    mScaleGestureDetector.onTouchEvent(event);
                    return false;
                }
            });
    
            mPhotoAdapter = new PhotoAdapter(this, 1000);
            mRecyclerView.setAdapter(mPhotoAdapter);
    
            mPhotoAdapter.dataSetChanged();
        }
    
        private int getSpanCountIndex(int spanCount) {
            int index = 0;
            for (int i = 0; i < ZOOM.length; i++) {
                if (spanCount == ZOOM[i]) {
                    index = i;
                }
            }
            return index;
        }
    }

MainActivity's layout:

<?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MainActivity">
    
        <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/recycler_view"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    
    </RelativeLayout>

RecyclerView's adapter，PhotosAdapter:

import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    
    import androidx.appcompat.widget.AppCompatTextView;
    import androidx.fragment.app.FragmentActivity;
    import androidx.recyclerview.widget.RecyclerView;
    
    import com.davemorrissey.labs.subscaleview.ImageSource;
    import com.davemorrissey.labs.subscaleview.SubsamplingScaleImageView;
    
    public class PhotoAdapter extends RecyclerView.Adapter<PhotoAdapter.PhotoViewHolder> {
        private String TAG = "ZHANGPHIL";
    
        private int itemCount;
    
        public PhotoAdapter(FragmentActivity activity, int itemCount) {
            this.itemCount = itemCount;
        }
    
        @Override
        public PhotoViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.photo, parent, false);
            PhotoViewHolder holder = new PhotoViewHolder(view);
            return holder;
        }
    
        @Override
        public void onBindViewHolder(PhotoViewHolder holder, int position) {
            holder.textView.setText(String.valueOf(position));
            holder.imageView.setImage(ImageSource.resource(R.mipmap.android));
            holder.imageView.setZoomEnabled(false);
        }
    
        @Override
        public int getItemCount() {
            return itemCount;
        }
    
        public class PhotoViewHolder extends RecyclerView.ViewHolder {
            public SubsamplingScaleImageView imageView;
            public AppCompatTextView textView;
    
            public PhotoViewHolder(View itemView) {
                super(itemView);
                imageView = itemView.findViewById(R.id.image);
                textView = itemView.findViewById(R.id.text);
            }
        }
    
        public void dataSetChanged() {
            notifyDataSetChanged();
        }
    }

PhotosAdapter's layout:

<?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="1dp"
        android:layout_marginTop="10dp"
        android:layout_marginRight="1dp">
    
        <com.davemorrissey.labs.subscaleview.SubsamplingScaleImageView
            android:id="@+id/image"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_alignParentTop="true"
            android:layout_centerHorizontal="true" />
    
        <androidx.appcompat.widget.AppCompatTextView
            android:id="@+id/text"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_below="@id/image"
            android:autoSizeMinTextSize="5dp"
            android:autoSizeTextType="uniform"
            android:gravity="center_horizontal"
            android:maxLines="1"
            android:text="-.-"
            android:textColor="@android:color/black" />
    </RelativeLayout>

android.png

![8164b371f4c6408b9635956334561f42.png][]

引用：

implementation 'androidx.appcompat:appcompat:1.6.1'
        implementation 'com.davemorrissey.labs:subsampling-scale-image-view-androidx:3.10.0'

pinch to zoom 2 columns：

![82b0b414f4154136ae320b45655f8348.png][]

pinch to zoom 3 columns：

![2b2c6a8d10614fbe82d277829c7d9723.png][]

pinch to zoom 8 columns：

![8e27172ffefd4542943ededdb00bed74.png][]

pinch to zoom 15 columns：

![8c0c6592adf54e27b63560934fa7cb15.png][]

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