我正在尝试使用 asyntask 在后台加载 webview，同时显示启动画面，当 webview 加载完成时，我希望启动画面消失并显示 webview。出于某种原因，当我尝试在模拟器中编译和运行代码时，我在 LogCat 中遇到了很多错误。
主 Activity .java
package dk.zerone.vuc;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.util.Log;
import android.view.Menu;
import android.webkit.WebView;
import android.webkit.WebViewClient;
public class MainActivity extends Activity {
public final boolean networkCheck() {
ConnectivityManager connec = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
if ( connec.getNetworkInfo(0).getState() == NetworkInfo.State.CONNECTED ||
connec.getNetworkInfo(0).getState() == NetworkInfo.State.CONNECTING ||
connec.getNetworkInfo(1).getState() == NetworkInfo.State.CONNECTING ||
connec.getNetworkInfo(1).getState() == NetworkInfo.State.CONNECTED ) {
return true;
} else if (connec.getNetworkInfo(0).getState() == NetworkInfo.State.DISCONNECTED || connec.getNetworkInfo(1).getState() == NetworkInfo.State.DISCONNECTED ) {
return false;
}
return false;
}
// The definition of our task class
private class LoadWebView extends AsyncTask<String, Integer, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
}
protected String doInBackground(String... params) {
String url = params[0];
WebView webview = new WebView(MainActivity.this);
webview.loadUrl(url);
Log.i("WebView", "doInBackground: Done loading url.");
return "";
}
protected void onPostExecute(String result) {
super.onPostExecute(result);
}
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
/* Splash screen */
setContentView(R.layout.splash);
if(networkCheck()) {
//Instantiating the webview, occupies the whole screen.
//WebView webview = new WebView(this);
//webview.loadUrl("http://mobil.vucfyn.dk/mobil");
new LoadWebView().execute("http://mobil.vucfyn.dk/mobil");
setContentView(R.layout.webview);
Log.i("WebView", "Execute asyntask");
/*webview.setWebViewClient(new WebViewClient() {
@Override
public void onPageFinished(WebView view, String url) {
//super.onPageFinished(view, url);
Log.i("WebView", "Finished loading.");
setContentView(R.layout.webview);
}
});*/
} else {
AlertDialog alertDialog = new AlertDialog.Builder(MainActivity.this).create();
alertDialog.setTitle("Fejl");
alertDialog.setMessage("Ingen forbindelse til internettet");
alertDialog.setButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
}
});
alertDialog.show();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}
来自 LogCat 的错误消息:
08-25 11:32:11.544: D/dalvikvm(549): GC_FOR_ALLOC freed 67K, 3% free 10191K/10503K, paused 60ms
08-25 11:32:11.563: I/dalvikvm-heap(549): Grow heap (frag case) to 11.036MB for 1048592-byte allocation
08-25 11:32:11.633: D/dalvikvm(549): GC_CONCURRENT freed 1K, 4% free 11214K/11591K, paused 6ms+3ms
08-25 11:32:11.713: I/WebView(549): SetContentView webview
08-25 11:32:11.733: I/WebView(549): Execute asyntask
08-25 11:32:11.923: D/gralloc_goldfish(549): Emulator without GPU emulation detected.
08-25 11:32:12.593: W/dalvikvm(549): threadid=11: thread exiting with uncaught exception (group=0x409961f8)
08-25 11:32:12.646: E/AndroidRuntime(549): FATAL EXCEPTION: AsyncTask #1
08-25 11:32:12.646: E/AndroidRuntime(549): java.lang.RuntimeException: An error occured while executing doInBackground()
08-25 11:32:12.646: E/AndroidRuntime(549): at android.os.AsyncTask$3.done(AsyncTask.java:278)
08-25 11:32:12.646: E/AndroidRuntime(549): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
08-25 11:32:12.646: E/AndroidRuntime(549): at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
08-25 11:32:12.646: E/AndroidRuntime(549): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
08-25 11:32:12.646: E/AndroidRuntime(549): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
08-25 11:32:12.646: E/AndroidRuntime(549): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:208)
08-25 11:32:12.646: E/AndroidRuntime(549): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
08-25 11:32:12.646: E/AndroidRuntime(549): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
08-25 11:32:12.646: E/AndroidRuntime(549): at java.lang.Thread.run(Thread.java:856)
08-25 11:32:12.646: E/AndroidRuntime(549): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
08-25 11:32:12.646: E/AndroidRuntime(549): at android.os.Handler.<init>(Handler.java:121)
08-25 11:32:12.646: E/AndroidRuntime(549): at android.webkit.WebView$PrivateHandler.<init>(WebView.java:8211)
08-25 11:32:12.646: E/AndroidRuntime(549): at android.webkit.WebView.<init>(WebView.java:437)
08-25 11:32:12.646: E/AndroidRuntime(549): at android.webkit.WebView.<init>(WebView.java:1040)
08-25 11:32:12.646: E/AndroidRuntime(549): at android.webkit.WebView.<init>(WebView.java:1029)
08-25 11:32:12.646: E/AndroidRuntime(549): at android.webkit.WebView.<init>(WebView.java:1019)
08-25 11:32:12.646: E/AndroidRuntime(549): at android.webkit.WebView.<init>(WebView.java:1010)
08-25 11:32:12.646: E/AndroidRuntime(549): at dk.zerone.vuc.MainActivity$LoadWebView.doInBackground(MainActivity.java:42)
08-25 11:32:12.646: E/AndroidRuntime(549): at dk.zerone.vuc.MainActivity$LoadWebView.doInBackground(MainActivity.java:1)
08-25 11:32:12.646: E/AndroidRuntime(549): at android.os.AsyncTask$2.call(AsyncTask.java:264)
08-25 11:32:12.646: E/AndroidRuntime(549): at java.util.concurrent.FutureTask$Sync.innerRun (FutureTask.java:305)
08-25 11:32:12.646: E/AndroidRuntime(549): ... 5 more
08-25 11:32:16.363: I/Process(549): Sending signal. PID: 549 SIG: 9
我不知道出了什么问题，非常感谢任何帮助。
更新:
package dk.zerone.vuc;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.graphics.Color;
import android.view.Menu;
import android.view.View;
import android.webkit.WebView;
import android.webkit.WebViewClient;
public class MainActivity extends Activity {
public final boolean networkCheck() {
ConnectivityManager connec = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
if ( connec.getNetworkInfo(0).getState() == NetworkInfo.State.CONNECTED ||
connec.getNetworkInfo(0).getState() == NetworkInfo.State.CONNECTING ||
connec.getNetworkInfo(1).getState() == NetworkInfo.State.CONNECTING ||
connec.getNetworkInfo(1).getState() == NetworkInfo.State.CONNECTED ) {
return true;
} else if (connec.getNetworkInfo(0).getState() == NetworkInfo.State.DISCONNECTED || connec.getNetworkInfo(1).getState() == NetworkInfo.State.DISCONNECTED ) {
return false;
}
return false;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
/* Splash screen */
setContentView(R.layout.splash);
if(networkCheck()) {
String url = "http://mobil.vucfyn.dk/mobil";
final WebView webview;
webview = new WebView(MainActivity.this);
webview.loadUrl(url);
webview.setWebViewClient(new WebViewClient() {
@Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
//view.loadUrl(url);
return false;
}
@Override
public void onPageFinished(WebView view, String url) {
super.onPageFinished(view, url);
setContentView(webview);
}
});
} else {
AlertDialog alertDialog = new AlertDialog.Builder(MainActivity.this).create();
alertDialog.setTitle("Fejl");
alertDialog.setMessage("Ingen forbindelse til internettet");
alertDialog.setButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
}
});
alertDialog.show();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}
最佳答案
为什么要使用 AsyncTask 这可以很容易地实现...
最好用这个
WebView webview = new WebView(MainActivity.this);
webview.loadUrl(url);
webview.setWebViewClient(new WebViewClient() {
@Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
view.loadUrl(url);
return false;
}
@Override
public void onPageFinished(WebView view, String url) {
super.onPageFinished(view, url);
//------>> EXIT YOUR SPLASH SCREEN HERE
}
});
关于android - WebView LoadUrl() 在后台使用 asynctask -，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/12121702/