RxAndroid、RxJava的fromCallable更新数据加载到ListView简例

RxAndroid、RxJava的fromCallable更新数据加载到ListView简例

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.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 com.lzy.okgo.OkGo; import java.util.ArrayList; import java.util.UUID; import java.util.concurrent.Callable; import io.reactivex.Observable; import io.reactivex.android.schedulers.AndroidSchedulers; import io.reactivex.observers.DisposableObserver; import io.reactivex.schedulers.Schedulers; 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; @Override public void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); 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); } }); // PublishSubject mEmitter = PublishSubject.create(); // mEmitter.map(new Function<Object, Bitmap>() { // @Override // public Bitmap apply(Object o) throws Exception { // String url= (String) o; // Bitmap bmp=loadingBitmap(url); // return bmp; // } // }) // .subscribeOn(Schedulers.io()) // .observeOn(AndroidSchedulers.mainThread()) // .subscribe(mObserver); } //假设这里每次都是新启一个耗时操作 private void addItem(final String url) { Observable.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 Response response = OkGo.get(url).tag(TAG).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(Bitmap io) { items.add(io); } @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(); OkGo.getInstance().cancelTag(TAG); } }

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> 

代码运行结果：

致谢：

冯祖学对本文有重大贡献！