通过 URL 下载图片并在点击按钮时显示在屏幕上
Download image through URL and show it on the Screen when clicked on the button
我正在尝试在单击按钮时在模拟器上显示图像。它是如何工作的，我提供了一个 URL 图像，所以当单击按钮时，相应的图像应该显示在模拟器上，但我在这里没有得到任何图像。
Java代码
package com.example.download;
import androidx.appcompat.app.AppCompatActivity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ImageView;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.concurrent.ExecutionException;
public class MainActivity extends AppCompatActivity {
ImageView imageView;
public void downLoad(View view)
{
ImgDownloader task = new ImgDownloader();
Bitmap myImage;
try {
myImage=task.execute("https://upload.wikimedia.org/wikipedia/en/a/aa/Bart_Simpson_200px.png").get();
imageView.setImageBitmap(myImage);
} catch (Exception e) {
e.printStackTrace();
}
Log.i("Button","Pressed");
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
imageView = (ImageView) findViewById(R.id.imageView);
}
public static class ImgDownloader extends AsyncTask<String, Void, Bitmap>
{
@Override
protected Bitmap doInBackground(String... urls) {
try {
URL url= new URL(urls[0]);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.connect();
InputStream inputStream = connection.getInputStream();
Bitmap myBitmap = BitmapFactory.decodeStream(inputStream);
return myBitmap;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}
}
布局
2020-09-09 07:52:03.931 13065-13129/com.example.download W/System.err: java.net.UnknownHostException: Unable to resolve host "upload.wikimedia.org": No address associated with hostname
2020-09-09 07:52:03.932 13065-13129/com.example.download W/System.err: at java.net.Inet6AddressImpl.lookupHostByName(Inet6AddressImpl.java:156)
2020-09-09 07:52:03.934 13065-13129/com.example.download W/System.err: at java.net.Inet6AddressImpl.lookupAllHostAddr(Inet6AddressImpl.java:103)
2020-09-09 07:52:03.934 13065-13129/com.example.download W/System.err: at java.net.InetAddress.getAllByName(InetAddress.java:1152)
2020-09-09 07:52:03.935 13065-13129/com.example.download W/System.err: at com.android.okhttp.Dns.lookup(Dns.java:41)
2020-09-09 07:52:03.936 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:178)
2020-09-09 07:52:03.936 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.http.RouteSelector.nextProxy(RouteSelector.java:144)
2020-09-09 07:52:03.938 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.http.RouteSelector.next(RouteSelector.java:86)
2020-09-09 07:52:03.938 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.http.StreamAllocation.findConnection(StreamAllocation.java:176)
2020-09-09 07:52:03.938 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.http.StreamAllocation.findHealthyConnection(StreamAllocation.java:128)
2020-09-09 07:52:03.939 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.http.StreamAllocation.newStream(StreamAllocation.java:97)
2020-09-09 07:52:03.940 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:289)
2020-09-09 07:52:03.940 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:232)
2020-09-09 07:52:03.941 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.huc.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:465)
2020-09-09 07:52:03.942 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.huc.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:131)
2020-09-09 07:52:03.942 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.huc.DelegatingHttpsURLConnection.connect(DelegatingHttpsURLConnection.java:90)
2020-09-09 07:52:03.943 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.huc.HttpsURLConnectionImpl.connect(HttpsURLConnectionImpl.java:30)
2020-09-09 07:52:03.943 13065-13129/com.example.download W/System.err: at com.example.download.MainActivity$ImgDownloader.doInBackground(MainActivity.java:55)
2020-09-09 07:52:03.944 13065-13129/com.example.download W/System.err: at com.example.download.MainActivity$ImgDownloader.doInBackground(MainActivity.java:48)
2020-09-09 07:52:03.946 13065-13129/com.example.download W/System.err: at android.os.AsyncTask.call(AsyncTask.java:394)
2020-09-09 07:52:03.947 13065-13129/com.example.download W/System.err: at java.util.concurrent.FutureTask.run(FutureTask.java:266)
2020-09-09 07:52:03.947 13065-13129/com.example.download W/System.err: at android.os.AsyncTask$SerialExecutor.run(AsyncTask.java:305)
2020-09-09 07:52:03.948 13065-13129/com.example.download W/System.err: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
2020-09-09 07:52:03.949 13065-13129/com.example.download W/System.err: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
2020-09-09 07:52:03.950 13065-13129/com.example.download W/System.err: at java.lang.Thread.run(Thread.java:923)
2020-09-09 07:52:03.951 13065-13129/com.example.download W/System.err: Caused by: android.system.GaiException: android_getaddrinfo failed: EAI_NODATA (No address associated with hostname)
2020-09-09 07:52:03.953 13065-13129/com.example.download W/System.err: at libcore.io.Linux.android_getaddrinfo(Native Method)
2020-09-09 07:52:03.954 13065-13129/com.example.download W/System.err: at libcore.io.ForwardingOs.android_getaddrinfo(ForwardingOs.java:73)
2020-09-09 07:52:03.954 13065-13129/com.example.download W/System.err: at libcore.io.BlockGuardOs.android_getaddrinfo(BlockGuardOs.java:202)
2020-09-09 07:52:03.954 13065-13129/com.example.download W/System.err: at libcore.io.ForwardingOs.android_getaddrinfo(ForwardingOs.java:73)
2020-09-09 07:52:03.955 13065-13129/com.example.download W/System.err: at java.net.Inet6AddressImpl.lookupHostByName(Inet6AddressImpl.java:135)
2020-09-09 07:52:03.956 13065-13129/com.example.download W/System.err: ... 23 more
2020-09-09 07:52:03.958 13065-13065/com.example.download I/Button: Pressed
2020-09-09 07:52:03.964 13065-13065/com.example.download I/Choreographer: Skipped 1207 frames! The application may be doing too much work on its main thread.
2020-09-09 07:52:03.988 13065-13117/com.example.download I/OpenGLRenderer: Davey! duration=20137ms; Flags=0, IntendedVsync=18050067477460, Vsync=18070184143322, OldestInputEvent=9223372036854775807, NewestInputEvent=0, HandleInputStart=18070186401860, AnimationStart=18070186512760, PerformTraversalsStart=18070187352960, DrawStart=18070187859860, SyncQueued=18070190416860, SyncStart=18070194709860, IssueDrawCommandsStart=18070195078060, SwapBuffers=18070198414760, FrameCompleted=18070209020960, DequeueBufferDuration=1898300, QueueBufferDuration=3621000, GpuCompleted=0,
清单
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.download">
<uses-permission android:name="android.permission.INTERNET"/>
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme"
android:usesCleartextTraffic="true"
android:networkSecurityConfig="@xml/network_security_config">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
network_security_config.xml
<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
<domain-config cleartextTrafficPermitted="true">
<domain includeSubdomains="true">secure.example.com</domain>
</domain-config>
</network-security-config>
XML 文件
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="@+id/imageView"
android:layout_width="match_parent"
android:layout_height="759dp"
android:layout_below="@+id/button"
android:layout_marginTop="-4dp"
android:layout_marginBottom="5dp" />
<Button
android:id="@+id/button"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="downLoad"
android:text="Button" />
</RelativeLayout>
</androidx.constraintlayout.widget.ConstraintLayout>
EAI_NODATA (No address associated with hostname)
通常意味着您没有网络访问权限。所以请检查您的 wifi 或网络连接
您的网络似乎不可用。根据this，尝试重新连接wifi连接或重启你的模拟器。
我正在尝试在单击按钮时在模拟器上显示图像。它是如何工作的，我提供了一个 URL 图像，所以当单击按钮时，相应的图像应该显示在模拟器上，但我在这里没有得到任何图像。
Java代码
package com.example.download;
import androidx.appcompat.app.AppCompatActivity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ImageView;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.concurrent.ExecutionException;
public class MainActivity extends AppCompatActivity {
ImageView imageView;
public void downLoad(View view)
{
ImgDownloader task = new ImgDownloader();
Bitmap myImage;
try {
myImage=task.execute("https://upload.wikimedia.org/wikipedia/en/a/aa/Bart_Simpson_200px.png").get();
imageView.setImageBitmap(myImage);
} catch (Exception e) {
e.printStackTrace();
}
Log.i("Button","Pressed");
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
imageView = (ImageView) findViewById(R.id.imageView);
}
public static class ImgDownloader extends AsyncTask<String, Void, Bitmap>
{
@Override
protected Bitmap doInBackground(String... urls) {
try {
URL url= new URL(urls[0]);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.connect();
InputStream inputStream = connection.getInputStream();
Bitmap myBitmap = BitmapFactory.decodeStream(inputStream);
return myBitmap;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}
}
布局
2020-09-09 07:52:03.931 13065-13129/com.example.download W/System.err: java.net.UnknownHostException: Unable to resolve host "upload.wikimedia.org": No address associated with hostname
2020-09-09 07:52:03.932 13065-13129/com.example.download W/System.err: at java.net.Inet6AddressImpl.lookupHostByName(Inet6AddressImpl.java:156)
2020-09-09 07:52:03.934 13065-13129/com.example.download W/System.err: at java.net.Inet6AddressImpl.lookupAllHostAddr(Inet6AddressImpl.java:103)
2020-09-09 07:52:03.934 13065-13129/com.example.download W/System.err: at java.net.InetAddress.getAllByName(InetAddress.java:1152)
2020-09-09 07:52:03.935 13065-13129/com.example.download W/System.err: at com.android.okhttp.Dns.lookup(Dns.java:41)
2020-09-09 07:52:03.936 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:178)
2020-09-09 07:52:03.936 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.http.RouteSelector.nextProxy(RouteSelector.java:144)
2020-09-09 07:52:03.938 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.http.RouteSelector.next(RouteSelector.java:86)
2020-09-09 07:52:03.938 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.http.StreamAllocation.findConnection(StreamAllocation.java:176)
2020-09-09 07:52:03.938 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.http.StreamAllocation.findHealthyConnection(StreamAllocation.java:128)
2020-09-09 07:52:03.939 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.http.StreamAllocation.newStream(StreamAllocation.java:97)
2020-09-09 07:52:03.940 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:289)
2020-09-09 07:52:03.940 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:232)
2020-09-09 07:52:03.941 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.huc.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:465)
2020-09-09 07:52:03.942 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.huc.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:131)
2020-09-09 07:52:03.942 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.huc.DelegatingHttpsURLConnection.connect(DelegatingHttpsURLConnection.java:90)
2020-09-09 07:52:03.943 13065-13129/com.example.download W/System.err: at com.android.okhttp.internal.huc.HttpsURLConnectionImpl.connect(HttpsURLConnectionImpl.java:30)
2020-09-09 07:52:03.943 13065-13129/com.example.download W/System.err: at com.example.download.MainActivity$ImgDownloader.doInBackground(MainActivity.java:55)
2020-09-09 07:52:03.944 13065-13129/com.example.download W/System.err: at com.example.download.MainActivity$ImgDownloader.doInBackground(MainActivity.java:48)
2020-09-09 07:52:03.946 13065-13129/com.example.download W/System.err: at android.os.AsyncTask.call(AsyncTask.java:394)
2020-09-09 07:52:03.947 13065-13129/com.example.download W/System.err: at java.util.concurrent.FutureTask.run(FutureTask.java:266)
2020-09-09 07:52:03.947 13065-13129/com.example.download W/System.err: at android.os.AsyncTask$SerialExecutor.run(AsyncTask.java:305)
2020-09-09 07:52:03.948 13065-13129/com.example.download W/System.err: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
2020-09-09 07:52:03.949 13065-13129/com.example.download W/System.err: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
2020-09-09 07:52:03.950 13065-13129/com.example.download W/System.err: at java.lang.Thread.run(Thread.java:923)
2020-09-09 07:52:03.951 13065-13129/com.example.download W/System.err: Caused by: android.system.GaiException: android_getaddrinfo failed: EAI_NODATA (No address associated with hostname)
2020-09-09 07:52:03.953 13065-13129/com.example.download W/System.err: at libcore.io.Linux.android_getaddrinfo(Native Method)
2020-09-09 07:52:03.954 13065-13129/com.example.download W/System.err: at libcore.io.ForwardingOs.android_getaddrinfo(ForwardingOs.java:73)
2020-09-09 07:52:03.954 13065-13129/com.example.download W/System.err: at libcore.io.BlockGuardOs.android_getaddrinfo(BlockGuardOs.java:202)
2020-09-09 07:52:03.954 13065-13129/com.example.download W/System.err: at libcore.io.ForwardingOs.android_getaddrinfo(ForwardingOs.java:73)
2020-09-09 07:52:03.955 13065-13129/com.example.download W/System.err: at java.net.Inet6AddressImpl.lookupHostByName(Inet6AddressImpl.java:135)
2020-09-09 07:52:03.956 13065-13129/com.example.download W/System.err: ... 23 more
2020-09-09 07:52:03.958 13065-13065/com.example.download I/Button: Pressed
2020-09-09 07:52:03.964 13065-13065/com.example.download I/Choreographer: Skipped 1207 frames! The application may be doing too much work on its main thread.
2020-09-09 07:52:03.988 13065-13117/com.example.download I/OpenGLRenderer: Davey! duration=20137ms; Flags=0, IntendedVsync=18050067477460, Vsync=18070184143322, OldestInputEvent=9223372036854775807, NewestInputEvent=0, HandleInputStart=18070186401860, AnimationStart=18070186512760, PerformTraversalsStart=18070187352960, DrawStart=18070187859860, SyncQueued=18070190416860, SyncStart=18070194709860, IssueDrawCommandsStart=18070195078060, SwapBuffers=18070198414760, FrameCompleted=18070209020960, DequeueBufferDuration=1898300, QueueBufferDuration=3621000, GpuCompleted=0,
清单
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.download">
<uses-permission android:name="android.permission.INTERNET"/>
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme"
android:usesCleartextTraffic="true"
android:networkSecurityConfig="@xml/network_security_config">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
network_security_config.xml
<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
<domain-config cleartextTrafficPermitted="true">
<domain includeSubdomains="true">secure.example.com</domain>
</domain-config>
</network-security-config>
XML 文件
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="@+id/imageView"
android:layout_width="match_parent"
android:layout_height="759dp"
android:layout_below="@+id/button"
android:layout_marginTop="-4dp"
android:layout_marginBottom="5dp" />
<Button
android:id="@+id/button"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="downLoad"
android:text="Button" />
</RelativeLayout>
</androidx.constraintlayout.widget.ConstraintLayout>
EAI_NODATA (No address associated with hostname)
通常意味着您没有网络访问权限。所以请检查您的 wifi 或网络连接
您的网络似乎不可用。根据this，尝试重新连接wifi连接或重启你的模拟器。