Table of contents
RXJava Thinking Download Image
Why learn RxJava?
-
Change thinking (responsive programming thinking), improve programming efficiency
Official website: ReactiveX
What is Reactive Programming?
[Based on the response of the previous layer to affect the changes of the next layer]
Reactive programming is a programming paradigm oriented towards data flow and change propagation. This means that static or dynamic data flows can be easily expressed in a programming language, and the associated computational model will automatically propagate changing values through the data flow
RXJava Thinking Download Image
Step 1: Add dependency packages
//RxAndroid的依赖包
implementation 'io.reactivex.rxjava2:rxandroid:2.0.1'
//RxJava的依赖包
implementation 'io.reactivex.rxjava2:rxjava:2.0.7'Step 2: Enable network permissions
<!--开启网络权限-->
<uses-permission android:name="android.permission.INTERNET"/>Step Three: Page Layout
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity"
android:orientation="vertical">
<!--下载图片-->
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="下载图片"
android:onClick="loadDownImage" />
<!--Rxjava来显示图片-->
<ImageView
android:id="@+id/image"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
</LinearLayout>Step 4: RXJava downloads/displays pictures (MainActivity code)
package com.example.rxjavastudy;
import androidx.appcompat.app.AppCompatActivity;
import android.annotation.SuppressLint;
import android.app.ProgressDialog;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageView;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import io.reactivex.Observable;
import io.reactivex.Observer;
import io.reactivex.android.schedulers.AndroidSchedulers;
import io.reactivex.disposables.Disposable;
import io.reactivex.functions.Function;
import io.reactivex.schedulers.Schedulers;
public class MainActivity extends AppCompatActivity {
//网络图片的链接地址
private final String PATH = "https://image.baidu.com/search/down?tn=download&word=download&ie=utf8&fr" +
"=detail&url=https%3A%2F%2Fgimg2.baidu.com%2Fimage_search%2Fsrc%3Dhttp%253A%252F%252Fpic1.win4000." +
"com%252Fwallpaper%252F7%252F57ec72987b140.jpg%26refer%3Dhttp%253A%252F%252Fpic1.win4000.com%26ap" +
"p%3D2002%26size%3Df9999%2C10000%26q%3Da80%26n%3D0%26g%3D0n%26fmt%3Dauto%3Fsec%3D1663469947%26t%3Df1" +
"cb7822473a7224f3ae863f7d7082ee&thumburl=https%3A%2F%2Fimg2.baidu.com%2Fit%2Fu%3D791640261%2C44080610%" +
"26fm%3D253%26fmt%3Dauto%26app%3D120%26f%3DJPEG%3Fw%3D1280%26h%3D800";
//弹出加载框（正在加载中.....）
private ProgressDialog progressDialog;
//ImageView控件，用来显示图片
private ImageView image;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//初始化ImageView
image=findViewById(R.id.image);
}
public void loadDownImage(View view) {
//起点-创建被观察者 通过just完成起点流向终点的操作
//TODO 第二步
Observable.just(PATH)
//需求 1：图片下载
//TODO 第三步
.map(new Function<String, Bitmap>() {
@Override
public Bitmap apply(String s) throws Exception {
try {
Thread.sleep(2000);//睡眠2s
URL url=new URL(PATH);//url
//请求服务器
HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
httpURLConnection.setConnectTimeout(5000);//设置请求时间为5s
//拿到服务器的响应码
int responseCode = httpURLConnection.getResponseCode();
if(responseCode==HttpURLConnection.HTTP_OK){//如果拿到200
InputStream inputStream=httpURLConnection.getInputStream();//获取输入流
Bitmap bitmap= BitmapFactory.decodeStream(inputStream);//解析输入流
return bitmap;
}
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
})
//需求2：给图片加水印
//TODO 第四步
.map(new Function<Bitmap, Bitmap>() {
@SuppressLint("ResourceAsColor")
@Override
public Bitmap apply(Bitmap bitmap) throws Exception {
Paint paint=new Paint();
paint.setColor(R.color.black);//颜色
paint.setTextSize(150);//文字大小
Bitmap bitmap1=drawTextToBitmap(bitmap,"这是一个水印",paint,100,150);
return bitmap1;
}
})
//需求3:打印日志
//TODO 第五步
.map(new Function<Bitmap, Bitmap>() {
@Override
public Bitmap apply(Bitmap bitmap) throws Exception {
System.out.println("日志："+bitmap);
return bitmap;
}
})
//给上面的分配异步线程
.subscribeOn(Schedulers.io())
//图片显示终点分配andorid主线程
.observeOn(AndroidSchedulers.mainThread())
//TODO 导火索 点燃了 开始执行
//关联起点和终点 创建观察者，并进行订阅
.subscribe(new Observer<Bitmap>() {
@Override
//终点-订阅成功
//TODO 第一步
public void onSubscribe(Disposable d) {
//显示加载框
progressDialog = new ProgressDialog(MainActivity.this);
progressDialog.setTitle("图片正在加载中...");
progressDialog.show();
}
@Override
//上一层给的响应
//TODO 第六步
public void onNext(Bitmap bitmap) {
//显示到控件上
image.setImageBitmap(bitmap);
}
@Override
//发生异常
public void onError(Throwable e) {
}
@Override
//链条结束
//TODO 第七步
public void onComplete() {
//隐藏加载框
if(progressDialog != null){
progressDialog.dismiss();
}
}
});
}
//水印
private final Bitmap drawTextToBitmap(Bitmap bitmap, String text, Paint paint, int paddingLeft, int paddingTop){
Bitmap.Config bitmapConfig = bitmap.getConfig();
paint.setDither(true);//获得更清晰的图片采样
paint.setFilterBitmap(true);//过滤
if(bitmapConfig == null){
bitmapConfig = Bitmap.Config.ARGB_8888;
}
Bitmap bitmap1 = bitmap.copy(bitmapConfig, true);
Canvas canvas = new Canvas(bitmap1);
canvas.drawText(text,paddingLeft,paddingTop,paint);
return bitmap1;
}
}Step 5: Effect
rxjava thinking download picture