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"?>
<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);
}
});
}
}