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() {

// @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() {

@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() {

@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：

android:id="@+id/activity_main"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:orientation="vertical">

android:id="@+id/button"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:text="按钮" />

android:id="@+id/listView"

android:layout_width="match_parent"

android:layout_height="match_parent" />

代码运行结果：

致谢：

冯祖学对本文有重大贡献！