RxAndroid、RxJava的PublishSubject改造Observable

Dear 丶 2023-10-17 12:03 10阅读 0赞

**RxAndroid、RxJava的PublishSubject改造Observable**

在附录1的基础上，用RxAndroid、RxJava的PublishSubject改造Observable，同时用OkHttp实现网络请求。  
改造集中在Java上层代码，如：

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.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.ArrayAdapter;
    import android.widget.Button;
    import android.widget.ImageView;
    import android.widget.ListView;
    
    import java.util.ArrayList;
    import java.util.UUID;
    import java.util.concurrent.Callable;
    
    import io.reactivex.android.schedulers.AndroidSchedulers;
    import io.reactivex.observers.DisposableObserver;
    import io.reactivex.schedulers.Schedulers;
    import io.reactivex.subjects.PublishSubject;
    import okhttp3.OkHttpClient;
    import okhttp3.Request;
    import okhttp3.Response;
    
    /**
     * 这个例子假设有一个应用场景：每点击一次按钮，然后就启动一个线程加载一个网络图片到ListView
     *
     * 本例的数据流动：button启动addItem，然后在addItem里面的fromCallable加载回来一个Bitmap。
     * 此时fromCallable返回的Bitmap经由RxAndroid机制自动链式丢给DisposableObserver的onNext
     */
    
    public class MainActivity extends Activity {
    
        private final String TAG = String.valueOf(UUID.randomUUID());
    
        private ArrayList items = new ArrayList<>();
        private ItemAdapter mAdapter;
    
        private PublishSubject mPublishSubject;
        private OkHttpClient mOkHttpClient;
    
        @Override
        public void onCreate(@Nullable Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            mOkHttpClient = new OkHttpClient();
            mPublishSubject = PublishSubject.create();
    
            ListView listView = (ListView) findViewById(R.id.listView);
            mAdapter = new ItemAdapter(this, R.layout.item);
            listView.setAdapter(mAdapter);
    
            final String url = "http://avatar.csdn.net/9/7/A/1_zhangphil.jpg";
            Button button = (Button) findViewById(R.id.button);
            button.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    //点击按钮增加一个ListView的item
                    addItem(url);
                }
            });
        }
    
        //假设这里每次都是新启一个耗时操作
        private void addItem(final String url) {
            mPublishSubject.fromCallable(new Callable<Bitmap>() {
                @Override
                public Bitmap call() throws Exception {
                    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();
                    }
    
                    return bmp;
                }
            }).subscribeOn(Schedulers.io())
                    .observeOn(AndroidSchedulers.mainThread())
                    .subscribe(new DisposableObserver<Bitmap>() {
    
                        @Override
                        public void onNext(@NonNull Bitmap bmp) {
                            items.add(bmp);
                        }
    
                        @Override
                        public void onComplete() {
                            mAdapter.notifyDataSetChanged();
                        }
    
                        @Override
                        public void onError(Throwable e) {
                            Log.e(TAG, e.toString(), e);
                        }
                    });
        }
    
    
        /**
         * 以下是常规的Android ListView数据添加和更新Adapter
         */
    
        private class ItemAdapter extends ArrayAdapter {
            private LayoutInflater inflater;
            private int resId;
    
            public ItemAdapter(@NonNull Context context, @LayoutRes int resource) {
                super(context, resource);
                inflater = LayoutInflater.from(context);
                resId = resource;
            }
    
            @NonNull
            @Override
            public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
                if (convertView == null) {
                    convertView = inflater.inflate(resId, null);
                }
    
                ImageView imageView = (ImageView) convertView.findViewById(R.id.image);
                imageView.setImageBitmap(getItem(position));
    
                return convertView;
            }
    
            @Nullable
            @Override
            public Bitmap getItem(int position) {
                Bitmap bmp = (Bitmap) items.get(position);
                return bmp;
            }
    
            @Override
            public int getCount() {
                return items.size();
            }
        }
    
        @Override
        protected void onDestroy() {
            super.onDestroy();
    
            //取消所有Okhttp的网络请求
            mOkHttpClient.dispatcher().cancelAll();
        }
    }

附录：  
1，《RxAndroid、RxJava的fromCallable更新数据加载到ListView简例》链接地址：[http://blog.csdn.net/zhangphil/article/details/66970893][http_blog.csdn.net_zhangphil_article_details_66970893]  
2，OkHttp:https://github.com/square/okhttp

[http_blog.csdn.net_zhangphil_article_details_66970893]: http://blog.csdn.net/zhangphil/article/details/66970893