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

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"?>

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() {            @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 getBitmapObservable(@NonNull final String url) {        return Observable.defer(new Callable>() {            @Override            public ObservableSource 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);            }        });    }}

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