Use Gallery to realize the special effects of photo dragging (source code attached)

Today I want to share a very simple function:

Use the Android native control Gallery to realize the special effects of photo dragging

The realization idea is as follows:

1. Define a Gallery control in the layout file
2. Due to the need to display multiple pictures, for convenience, I directly quoted Android native picture resources
3. Gallery is just a control. In order to bind the image data to the control, a custom adapter that inherits BaseAdapter is needed.

The source code is as follows:

1. Main activity and custom internal class ImageAdapter:

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageView;
import com.example.memorydemo.R;

public class SimpleGallery extends Activity {

    private static final String TAG = "SimpleGallery";

    @Override
    protected void onCreate(Bundle onSavedInstance) {
        super.onCreate(onSavedInstance);
        setContentView(R.layout.simple_gallery_layout);

        Gallery gallery = findViewById(R.id.gallery);
        gallery.setAdapter(new ImageAdapter(this));
    }

    private class ImageAdapter extends BaseAdapter {

        // 这里我们使用Android原生的资源图标
        private int[] imageIds = {
                android.R.drawable.btn_minus,
                android.R.drawable.btn_radio,
                android.R.drawable.ic_lock_idle_low_battery,
                android.R.drawable.ic_menu_camera };

        private Context mContext;

        public ImageAdapter(Context context) {
            mContext = context;
        }

        @Override
        public int getCount() {
            return imageIds.length;
        }

        @Override
        public Object getItem(int position) {
            return imageIds[position];
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
           ImageView imageView;
            if (convertView == null) {
                Log.i(TAG, "convertView is null, create new imageview");
                imageView = new ImageView(mContext);
            } else {
                Log.i(TAG, "Cast convertView to ImageView");
                imageView = (ImageView) convertView;
            }

            imageView.setImageResource(imageIds[position]);
            imageView.setScaleType(ImageView.ScaleType.FIT_XY);

            // 注意这里要用Gallery.LayoutParams作为布局参数类型，源码中给出了建议（Views given to the Gallery should use 
            // Gallery.LayoutParams s their ayout parameters type）
            // 由于Android原生图片很小，我将高度设置为 500，方便看效果
            imageView.setLayoutParams(new Gallery.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, 500));
            return imageView;
        }
    }
}

2. The layout file simple_gallery_layout.xml is as follows:

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

    <Gallery
            android:id="@+id/gallery"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

</LinearLayout>

note:

The Gallery control has been deprecated. It is recommended to use HorizontalScrollView and ViewPager instead, as explained in the source code:

@deprecated This widget is no longer supported. Other horizontally scrolling widgets include {@link HorizontalScrollView} and {@link android.support.v4.view.ViewPager} from the support library.

Later, I will share how the two controls, HorizontalScrollView and ViewPager, are used.

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