Android相册解决加载大量图片卡顿问题

来源：互联网发布：车载网络硬盘录像机编辑：程序博客网时间：2024/04/30 13:28

Android开发中加载相册是很常用的功能，但相册图片过多正常加载会产生卡顿，即便使用线程异步加载图片卡顿问题依然得不到改善。
正常代码：

public class AlbumAdapter extends ?{    @Override    public void onBindViewHolder(RecyclerView.ViewHolder holder, final int position) {        if(bitmap!=null){            线程加载图片        }        else            读取缓存    }}

卡顿原因是无论怎样优化读取IO都是费时的工作，adapter又会一次实例多个子项，导致加载的图片过多，内存占用率过高产生了卡顿。
优化代码：

public class AlbumActivity extends AppCompatActivity{    private RecyclerView mRecyclerView;    private List<PhotoItem> photoItemList;    private List<PhotoItem> selectItemList;    private int[] photoLayout;    private AlbumAdapter mAdapter;    private Handler handler;    private Button submit;    private GridLayoutManager gridLayoutManager;    private static final String[] STORE_IMAGES = {            MediaStore.Images.Media.DISPLAY_NAME, // 显示的名字            MediaStore.Images.Media.LATITUDE, // 维度            MediaStore.Images.Media.LONGITUDE, // 经度            MediaStore.Images.Media._ID, // id            MediaStore.Images.Media.BUCKET_ID, // dir id 目录            MediaStore.Images.Media.BUCKET_DISPLAY_NAME, // dir name 目录名字            MediaStore.Images.Media.DATA//路径    };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_album);        submit = (Button)findViewById(R.id.submit);        mRecyclerView = (RecyclerView)findViewById(R.id.list);        gridLayoutManager = new GridLayoutManager(this, 3);        mRecyclerView.setLayoutManager(gridLayoutManager);        mRecyclerView.setHasFixedSize(true);        photoLayout = new int[2];        photoLayout[0]=(ScreenHelper.getScreenWidth(this) - ScreenHelper.dp2px(this, 20)) / 3 - ScreenHelper.dp2px(this, 10);        photoLayout[1] = ScreenHelper.dp2px(this, 110);        gridLayoutManager.findFirstCompletelyVisibleItemPosition();        initPhoto();        notifySubmit();        mAdapter = new AlbumAdapter(mRecyclerView,photoItemList,selectItemList);        mAdapter.setOnItemClickListener(new OnItemClickListener() {            @Override            public void onItemClick(RecyclerView.ViewHolder viewHolder, int position) {                notifySubmit();            }        });        mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {            @Override            public void onScrollStateChanged(RecyclerView recyclerView, int newState) {                //停止滑动后缓存当前屏幕图片                if(newState == 0){                    new Thread(new Runnable() {                        @Override                        public void run() {                            for(int i=gridLayoutManager.findFirstVisibleItemPosition();i<gridLayoutManager.findLastVisibleItemPosition();i++){                                cacheBitmap(i);                            }                        }                    }).start();                }            }        });        mRecyclerView.setAdapter(mAdapter);        handler = new Handler(new Handler.Callback() {            @Override            public boolean handleMessage(Message msg) {                mAdapter.notifyImage((int)msg.obj);                return false;            }        });    }    private void initPhoto(){        photoItemList = new ArrayList<>();        selectItemList = (List<PhotoItem>)getIntent().getSerializableExtra(FinalHelper.IMAGE_PATH);        if(selectItemList == null)            selectItemList = new ArrayList<>();        String path="";        for(int i=0;i<selectItemList.size();i++){            path += selectItemList.get(i).getPath()+",";        }        Cursor cursor = MediaStore.Images.Media.query(getContentResolver(), MediaStore.Images.Media.EXTERNAL_CONTENT_URI, STORE_IMAGES,"width >0","date_modified desc");        cursor.moveToNext();        for (int i = 0; i < cursor.getCount(); i++) {            PhotoItem photoItem = new PhotoItem(cursor.getInt(3),path.indexOf(cursor.getString(6))!=-1?true:false,cursor.getString(0),cursor.getString(6));            photoItemList.add(photoItem);            cursor.moveToNext();        }        //从前往后存缓存缩略图  单线程轮播减少内存消耗确保屏幕不卡顿        new Thread(new Runnable() {            @Override            public void run() {                for(int i=0;i<photoItemList.size();i++){                    cacheBitmap(i);                }            }        }).start();    }    //缓存bitmap    public void cacheBitmap(int position){        if(CacheManager.get(photoItemList.get(position).getPath())==null){            Bitmap bitmap = ImageHelper.getSmallCropBitmap(photoItemList.get(position).getPath(), photoLayout[0], photoLayout[1]);            CacheManager.put(photoItemList.get(position).getPath(),bitmap);            Message message = new Message();            message.obj=position;            handler.sendMessage(message);        }    }    public void notifySubmit(){        if(selectItemList.size()>0){            submit.setBackgroundResource(R.drawable.bg_album_submit_enable);            submit.setText(getString(R.string.submit) + "(" + selectItemList.size() + ")");            submit.setTextColor(ContextCompat.getColor(this, R.color.white));            submit.setAlpha(1f);            submit.setClickable(true);        }        else {            submit.setBackgroundResource(R.drawable.bg_album_submit);            submit.setTextColor(ContextCompat.getColor(this, R.color.darkgray));            submit.setAlpha(.8f);            submit.setText(getString(R.string.submit));            submit.setClickable(false);        }    }    public void onSubmit(View view){        Intent intent = new Intent();        intent.putExtra(FinalHelper.IMAGE_PATH, (Serializable) selectItemList);        setResult(Activity.RESULT_OK, intent);        finish();    }    public void onBack(View view){        finish();    }    public void onCancel(View view){        finish();    }}

在读取相册的基本数据后，采用单线程轮播的方式顺序缓存图片缩率图，这样便解决了卡顿问题，在配合缓存类，再次加载相册就可以瞬间全部加载完毕，推荐使用开源的第三方库DiskLruCache实现图片的缩略图缓存。
QQ相册初次加载相册图片也是一张一张的，仿QQ相册实例：http://blog.csdn.net/lishengko/article/details/56495553

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