原因：java.lang.IllegalArgumentException：主机名不能为null

Question

我在代码中使用了four 字符串 。 通过组合first字符串， first字符串包含“ http:// ”， second字符串包含用户主机URL（由用户输入）， third fourth字符串包含“ /musics/a.mp3 ”， fourth字符串包含完整的URL，例如这个：

String fourth = first+second+third;

然后，我在AsyncTask的execute中使用fourth String，如下所示：

new JSONAsyncTask().execute(fourth);

我在下面看到错误。

日志：

10-07 06:17:15.934: E/AndroidRuntime(1194): FATAL EXCEPTION: AsyncTask #1
10-07 06:17:15.934: E/AndroidRuntime(1194): java.lang.RuntimeException: An error occured while executing doInBackground()
10-07 06:17:15.934: E/AndroidRuntime(1194):     at android.os.AsyncTask$3.done(AsyncTask.java:278)
10-07 06:17:15.934: E/AndroidRuntime(1194):     at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
10-07 06:17:15.934: E/AndroidRuntime(1194):     at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
10-07 06:17:15.934: E/AndroidRuntime(1194):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
10-07 06:17:15.934: E/AndroidRuntime(1194):     at java.util.concurrent.FutureTask.run(FutureTask.java:137)
10-07 06:17:15.934: E/AndroidRuntime(1194):     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:208)
10-07 06:17:15.934: E/AndroidRuntime(1194):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
10-07 06:17:15.934: E/AndroidRuntime(1194):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
10-07 06:17:15.934: E/AndroidRuntime(1194):     at java.lang.Thread.run(Thread.java:856)
10-07 06:17:15.934: E/AndroidRuntime(1194): Caused by: java.lang.IllegalArgumentException: Host name may not be null
10-07 06:17:15.934: E/AndroidRuntime(1194):     at org.apache.http.HttpHost.<init>(HttpHost.java:83)
10-07 06:17:15.934: E/AndroidRuntime(1194):     at org.apache.http.impl.client.AbstractHttpClient.determineTarget(AbstractHttpClient.java:497)
10-07 06:17:15.934: E/AndroidRuntime(1194):     at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
10-07 06:17:15.934: E/AndroidRuntime(1194):     at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
10-07 06:17:15.934: E/AndroidRuntime(1194):     at com.app.ifko.HomeActivity$JSONAsyncTask.doInBackground(HomeActivity.java:101)
10-07 06:17:15.934: E/AndroidRuntime(1194):     at com.app.ifko.HomeActivity$JSONAsyncTask.doInBackground(HomeActivity.java:1)
10-07 06:17:15.934: E/AndroidRuntime(1194):     at android.os.AsyncTask$2.call(AsyncTask.java:264)
10-07 06:17:15.934: E/AndroidRuntime(1194):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
10-07 06:17:15.934: E/AndroidRuntime(1194):     ... 5 more
10-07 06:17:22.764: E/WindowManager(1194): Activity com.app.ifko.HomeActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@416b80b0 that was originally added here
10-07 06:17:22.764: E/WindowManager(1194): android.view.WindowLeaked: Activity com.app.ifko.HomeActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@416b80b0 that was originally added here
10-07 06:17:22.764: E/WindowManager(1194):  at android.view.ViewRootImpl.<init>(ViewRootImpl.java:343)
10-07 06:17:22.764: E/WindowManager(1194):  at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:245)
10-07 06:17:22.764: E/WindowManager(1194):  at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:193)
10-07 06:17:22.764: E/WindowManager(1194):  at android.view.WindowManagerImpl$CompatModeWrapper.addView(WindowManagerImpl.java:118)
10-07 06:17:22.764: E/WindowManager(1194):  at android.view.Window$LocalWindowManager.addView(Window.java:537)
10-07 06:17:22.764: E/WindowManager(1194):  at android.app.Dialog.show(Dialog.java:274)
10-07 06:17:22.764: E/WindowManager(1194):  at com.app.ifko.HomeActivity$JSONAsyncTask.onPreExecute(HomeActivity.java:90)
10-07 06:17:22.764: E/WindowManager(1194):  at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:561)
10-07 06:17:22.764: E/WindowManager(1194):  at android.os.AsyncTask.execute(AsyncTask.java:511)
10-07 06:17:22.764: E/WindowManager(1194):  at com.app.ifko.HomeActivity.onCreate(HomeActivity.java:74)
10-07 06:17:22.764: E/WindowManager(1194):  at android.app.Activity.performCreate(Activity.java:4465)
10-07 06:17:22.764: E/WindowManager(1194):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
10-07 06:17:22.764: E/WindowManager(1194):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919)
10-07 06:17:22.764: E/WindowManager(1194):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)
10-07 06:17:22.764: E/WindowManager(1194):  at android.app.ActivityThread.access$600(ActivityThread.java:122)
10-07 06:17:22.764: E/WindowManager(1194):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)
10-07 06:17:22.764: E/WindowManager(1194):  at android.os.Handler.dispatchMessage(Handler.java:99)
10-07 06:17:22.764: E/WindowManager(1194):  at android.os.Looper.loop(Looper.java:137)
10-07 06:17:22.764: E/WindowManager(1194):  at android.app.ActivityThread.main(ActivityThread.java:4340)
10-07 06:17:22.764: E/WindowManager(1194):  at java.lang.reflect.Method.invokeNative(Native Method)
10-07 06:17:22.764: E/WindowManager(1194):  at java.lang.reflect.Method.invoke(Method.java:511)
10-07 06:17:22.764: E/WindowManager(1194):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
10-07 06:17:22.764: E/WindowManager(1194):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
10-07 06:17:22.764: E/WindowManager(1194):  at dalvik.system.NativeStart.main(Native Method)
10-07 06:17:24.144: I/Process(1194): Sending signal. PID: 1194 SIG: 9

活动代码：

public class HomeActivity extends Activity {

String first, second, third, fourth;
TextView etTextToSave;
private SharedPreferences  sharedprefs; 

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.home);

    etTextToSave = (TextView) findViewById(R.id.etTextToSave);      

    sharedprefs = getSharedPreferences("MyPrefs", MODE_PRIVATE);
    etTextToSave.setText(sharedprefs.getString("SharedPrefsData",""));

    second = etTextToSave.getText().toString();     

    first = "http://";
    third = "/musics/a.mp3";            
    fourth = first+second+third;

    .........................

    new JSONAsyncTask().execute(fourth);

}

Answer 1

如果URL的主机部分来自用户，则必须在使用URL构造URL之前对其进行验证。

不要调用new JSONAsyncTask().execute(fourth); 如果second为null。

Answer 2

如果要在onCreate()调用etTextToSave.getText() ，则返回的文本将是布局中默认存在的内容，而不是用户输入的内容。

如果您使用的是onclick侦听器或类似的侦听器，则不会显示代码，但如果使用的话，请将getText()移至单击处理程序。