OkHttpClient加载图片给DisposableObserver，CompositeDisposable调度控制后台任务队列简单代码

素颜马尾好姑娘i 2023-10-17 12:38 4阅读 0赞

**OkHttpClient加载图片给DisposableObserver，CompositeDisposable调度控制后台任务队列简单代码**

实现一个简单的功能，点击按钮，触发OkHttpClient加载图片给DisposableObserver，然后刷新ListView。全程有CompositeDisposable控制任务队列。  
  
  
布局文件：

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/activity_main"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">
    
        <Button
            android:id="@+id/button"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="按钮" />
    
        <ListView
            android:id="@+id/listView"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    
    </LinearLayout>

Java代码：

package zhangphil.app;
    
    import android.app.Activity;
    import android.content.Context;
    import android.graphics.Bitmap;
    import android.graphics.BitmapFactory;
    import android.os.Bundle;
    import android.support.annotation.LayoutRes;
    import android.support.annotation.NonNull;
    import android.support.annotation.Nullable;
    import android.util.Log;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.ArrayAdapter;
    import android.widget.ImageView;
    import android.widget.ListView;
    
    import java.util.ArrayList;
    import java.util.UUID;
    import java.util.concurrent.Callable;
    
    import io.reactivex.Observable;
    import io.reactivex.ObservableSource;
    import io.reactivex.android.schedulers.AndroidSchedulers;
    import io.reactivex.disposables.CompositeDisposable;
    import io.reactivex.observers.DisposableObserver;
    import io.reactivex.schedulers.Schedulers;
    
    import okhttp3.OkHttpClient;
    import okhttp3.Request;
    import okhttp3.Response;
    
    public class MainActivity extends Activity {
    
        private final String TAG = String.valueOf(UUID.randomUUID());
    
        private ArrayList mItems = new ArrayList<>();
        private ItemAdapter mAdapter;
    
        private OkHttpClient mOkHttpClient;
    
        private CompositeDisposable mCompositeDisposable = new CompositeDisposable();
    
        @Override
        public void onCreate(@Nullable Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            mOkHttpClient = new OkHttpClient();
    
            mAdapter = new ItemAdapter(this, -1);
            ListView listView = (ListView) findViewById(R.id.listView);
            listView.setAdapter(mAdapter);
    
            findViewById(R.id.button).setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    String url = "http://avatar.csdn.net/9/7/A/1_zhangphil.jpg";
                    addItems(url);
                }
            });
        }
    
        private void addItems(final String url) {
            DisposableObserver disposableObserver = new DisposableObserver<Bitmap>() {
    
                @Override
                public void onNext(@NonNull Bitmap bmp) {
                    Log.d(TAG, "onNext");
                    mItems.add(bmp);
                }
    
                @Override
                public void onComplete() {
                    Log.d(TAG, "onComplete");
                    mAdapter.notifyDataSetChanged();
                }
    
                @Override
                public void onError(Throwable e) {
                    Log.e(TAG, e.toString(), e);
                }
            };
    
            /**
             * 注意此处的写法！
             */
            mCompositeDisposable.add(
                    getBitmapObservable(url)
                            .subscribeOn(Schedulers.io())
                            .observeOn(AndroidSchedulers.mainThread())
                            .subscribeWith(disposableObserver)
            );
        }
    
    
        /**
         * 以下是常规的Android ListView数据添加和更新Adapter
         */
    
        private class ItemAdapter extends ArrayAdapter {
            private Context context;
    
            public ItemAdapter(@NonNull Context context, @LayoutRes int resource) {
                super(context, resource);
                this.context = context;
            }
    
            @NonNull
            @Override
            public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
                ImageView imageView = new ImageView(context);
                imageView.setImageBitmap(getItem(position));
                return imageView;
            }
    
            @Nullable
            @Override
            public Bitmap getItem(int position) {
                Bitmap bmp = (Bitmap) mItems.get(position);
                return bmp;
            }
    
            @Override
            public int getCount() {
                return mItems.size();
            }
        }
    
        @Override
        protected void onDestroy() {
            super.onDestroy();
    
            //取消所有Okhttp的网络请求
            mOkHttpClient.dispatcher().cancelAll();
    
            //如果退出程序，就清除后台任务
            mCompositeDisposable.clear();
        }
    
    
        private Observable<Bitmap> getBitmapObservable(@NonNull final String url) {
            return Observable.defer(new Callable<ObservableSource<Bitmap>>() {
                @Override
                public ObservableSource<Bitmap> call() throws Exception {
                    Thread.sleep(5000);
    
                    Bitmap bmp = null;
    
                    //同步方法返回观察者需要的数据结果
                    //在这里处理线程化的操作
    
                    Request request = new Request.Builder().url(url).build();
                    Response response = mOkHttpClient.newCall(request).execute();
                    try {
                        if (response.isSuccessful()) {
                            byte[] bytes = response.body().bytes();
                            bmp = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);
                        }
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
    
                    Log.d(TAG, "数据正确");
    
                    return Observable.just(bmp);
                }
            });
        }
    }