Question

应用程序工作（api 23测试也测试了kitkat），但没有显示，它应该显示图片（下载并将其放入视图）。由于我没有收到任何错误，我迷路了。我从android初学者书中寻找代码，并且他们建议在4.0（冰淇淋）上测试应用程序但是在该版本的android studio中没有推荐的版本。是不是因为android在最新API中使用HTTP和网络的方式发生了一些变化？

public class NetworkingActivity extends Activity {

ImageView img;

private InputStream OpenHttpConnection(String urlString)
        throws IOException
{
    InputStream in = null;
    int response = -1;

    URL url = new URL(urlString);
    URLConnection conn = url.openConnection();

    if (!(conn instanceof HttpURLConnection))
        throw new IOException("Not an HTTP connection");
    try{
        HttpURLConnection httpConn = (HttpURLConnection) conn;
        httpConn.setAllowUserInteraction(false);
        httpConn.setInstanceFollowRedirects(true);
        httpConn.setRequestMethod("GET");
        httpConn.connect();
        response = httpConn.getResponseCode();
        if (response == HttpURLConnection.HTTP_OK) {
            in = httpConn.getInputStream();
        }
    }
    catch (Exception ex)
    {
        Log.d("Networking", ex.getLocalizedMessage());
        throw new IOException("Error connecting");
    }
    return in;
}

private Bitmap DownloadImage(String URL)
{
    Bitmap bitmap = null;
    InputStream in = null;
    try {
        in = OpenHttpConnection(URL);
        bitmap = BitmapFactory.decodeStream(in);
        in.close();
    } catch (IOException e1) {
        Log.d("NetworkingActivity", e1.getLocalizedMessage());
    }
    return bitmap;
}

private class DownloadImageTask extends AsyncTask<String, Void, Bitmap> {
    protected Bitmap doInBackground(String... urls) {
        return DownloadImage(urls[0]);
    }

    protected void onPostExecute(Bitmap result) {
        ImageView img = (ImageView) findViewById(R.id.img);
        img.setImageBitmap(result);
    }
}

public void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    new DownloadImageTask().execute("http://www.mayoff.com/5-01cablecarDCP01934.jpg");

}
}

这是logcat：

AndroidManifest.xml文件：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="metropolitan.com.desetopredavanjeprotokoli10">

<uses-permission android:name="android.permission.INTERNET"/>

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity android:name=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

MainActivity类：

package metropolitan.com.desetopredavanjeprotokoli10;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
}
}

你走了：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout    xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">

<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Smor"
    android:layout_gravity="center"/>

<ImageView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/img"
    android:layout_gravity="center"/>
</RelativeLayout>

Answer 1

既然你是初学者，我建议你学习如何使用框架使用框架有很多好处，如果不是，你需要实现一些复杂的代码来处理，比如缓存，调整大小，避免内存崩溃，处理你所面临的几乎所有API等。

对于图像下载我建议

Picasso（我建议最多）

Glide

正常的Http请求

Volley

你也可以让我们Volley下载图片。当你开始学习时，它很难理解，但在你真正理解之后，我保证你不会使用常规HTTPURLConnection来处理任何HTTP请求

如果您需要上传进度，请告诉我我也会添加代码，尽管它很复杂。

编辑：

到目前为止，我已经测试了你的代码，它完全正常。我想为你添加它。

MainActivity

    ImageView img;

    private InputStream OpenHttpConnection(String urlString)
            throws IOException
    {
        InputStream in = null;
        int response = -1;

        URL url = new URL(urlString);
        URLConnection conn = url.openConnection();

        if (!(conn instanceof HttpURLConnection))
            throw new IOException("Not an HTTP connection");
        try{
            HttpURLConnection httpConn = (HttpURLConnection) conn;
            httpConn.setAllowUserInteraction(false);
            httpConn.setInstanceFollowRedirects(true);
            httpConn.setRequestMethod("GET");
            httpConn.connect();
            response = httpConn.getResponseCode();
            if (response == HttpURLConnection.HTTP_OK) {
                in = httpConn.getInputStream();
                Log.d("asd","OK");
            }else{
                Log.d("asd","error");
            }
        }
        catch (Exception ex)
        {
            Log.d("Networking", ex.getLocalizedMessage());
            throw new IOException("Error connecting");
        }
        return in;
    }

    private Bitmap DownloadImage(String URL)
    {
        Bitmap bitmap = null;
        InputStream in = null;
        try {
            in = OpenHttpConnection(URL);
            Log.d("in", String.valueOf(in));
            bitmap = BitmapFactory.decodeStream(in);
            in.close();
        } catch (IOException e1) {
            Log.d("NetworkingActivity", e1.getLocalizedMessage());
        }
        return bitmap;
    }

    private class DownloadImageTask extends AsyncTask<String, Void, Bitmap> {

        protected Bitmap doInBackground(String... urls) {
            Log.d("aSD","ASD");
            return DownloadImage(urls[0]);
        }

        protected void onPostExecute(Bitmap result) {
            ImageView img = (ImageView) findViewById(R.id.img);
            img.setImageBitmap(result);
        }
    }

    public void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        new DownloadImageTask().execute("http://www.mayoff.com/5-01cablecarDCP01934.jpg");

    }

activity_main.xml中

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.myapplication.MainActivity">

    <ImageView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/img"/>
</RelativeLayout>

最后将此添加到清单

    <uses-permission android:name="android.permission.INTERNET"/>

结果

如果确实无法正常工作，请考虑检查您的模拟器或设备网络连接。

Android网络简易应用

1 个答案: