Android超長圖顯示控件

先上代碼

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapRegionDecoder;
import android.graphics.Rect;
import android.support.annotation.AttrRes;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.AttributeSet;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;
import android.widget.ImageView;
import com.example.administrator.demo.ScreenUtil;
import java.io.IOException;
import java.io.InputStream;

/**
 * Created by WangPing on 2018/1/12.
 */

public class LongPicView extends FrameLayout {
    private RecyclerView picList;
    private Bitmap[] picArr;
    private int contentHeight;


    public LongPicView(@NonNull Context context) {
        super(context);
        init(context);
    }

    public LongPicView(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        init(context);
    }

    public LongPicView(@NonNull Context context, @Nullable AttributeSet attrs, @AttrRes int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init(context);
    }

    private void init(Context context) {
        int screenHeight = ScreenUtil.getScreenHeight(context);
        int statusHeight = ScreenUtil.getStatusHeight(context);
        int naviHeight = ScreenUtil.getNavigationBarHeight(context);
        contentHeight = screenHeight - statusHeight - naviHeight;

        picList = new RecyclerView(context);
        FrameLayout.LayoutParams params = new FrameLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
        params.gravity = Gravity.CENTER_HORIZONTAL;
        picList.setLayoutParams(params);


        picList.setLayoutManager(new LinearLayoutManager(context));
        this.addView(picList);
    }

    public void setImageSource(InputStream is) {
        BitmapFactory.Options tmpOptions = new BitmapFactory.Options();
        tmpOptions.inJustDecodeBounds = true;
        BitmapFactory.decodeStream(is, null, tmpOptions);
        int imageWidth = tmpOptions.outWidth;
        int imageHeight = tmpOptions.outHeight;
        int picListSize;
        if (imageHeight % contentHeight == 0) {
            picListSize = imageHeight / contentHeight;
        } else {
            picListSize = imageHeight / contentHeight + 1;
        }
        picArr = new Bitmap[picListSize];
        try {
            BitmapRegionDecoder bitmapRegionDecoder = BitmapRegionDecoder.newInstance(is, false);
            BitmapFactory.Options options = new BitmapFactory.Options();
            options.inPreferredConfig = Bitmap.Config.RGB_565;
            for (int i = 0; i < picListSize; i++) {
                Rect rect = new Rect();
                rect.left = 0;
                rect.top = contentHeight * i;
                rect.right = imageWidth;
                int clipHeight = contentHeight * (i + 1);
                if (clipHeight >= imageHeight) {
                    rect.bottom = imageHeight;
                } else {
                    rect.bottom = clipHeight;
                }
                Bitmap bitmap = bitmapRegionDecoder.decodeRegion(rect, options);
                picArr[i] = bitmap;
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        PicAdapter adapter = new PicAdapter();
        picList.setAdapter(adapter);
    }


    private class PicAdapter extends RecyclerView.Adapter<ViewHolder> {

        @Override
        public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            final ImageView image = new ImageView(parent.getContext());
            image.setScaleType(ImageView.ScaleType.FIT_XY);
            return new ViewHolder(image);
        }

        @Override
        public void onBindViewHolder(ViewHolder holder, int position) {
            ImageView iv = (ImageView) holder.itemView;
            iv.setImageBitmap(picArr[position]);
        }

        @Override
        public int getItemCount() {
            return picArr.length;
        }
    }

    static class ViewHolder extends RecyclerView.ViewHolder {

        ViewHolder(View itemView) {
            super(itemView);
        }
    }
}

原理是使用BitmapRegionDecoder來實現對圖片的區域選擇，通過Rect得到圖片中想要部分的Bitmap

將原圖拆分，再使用RecyclerView將圖片拼裝起來實現查看長圖的功能

本來是想做成新浪微博類似的查看長圖，但卡在了將圖片放大後再滑動時有部分滑不出來，暫時還沒想出怎麼完美解決，暫時就先放個閹割版的吧。