我有一个应用程序应该从服务器获取一些字符串，具体取决于网页，每次运行它都会崩溃。我不明白如何调试它，我尝试了很多变化。自从我搞砸了GUI以来，它开始崩溃，并且如果能提供任何帮助，还增加了切换视图的能力。
以下是代码：
public class MainActivity extends Activity implements TextToSpeech.OnInitListener, OnClickListener{
private WebView mWebview;
EditText addressBar;
String currentWebpage = "http://www.aljazeera.com/news/americas/2013/07/20137113200544375.html";
LinearLayout viewGroup = (LinearLayout) findViewById(R.id.linearview);
View main = (View) findViewById(R.layout.activity_main);
View readOut = (View) findViewById(R.layout.read_out);
@Override
public void onCreate(Bundle savedInstanceState) {
System.out.println("Showing Activity_Main...");
viewGroup.addView(View.inflate(this, R.layout.activity_main, null));
super.onCreate(savedInstanceState);
//setContentView(R.menu.main);
addressBar = (EditText)findViewById(R.id.addressBar);
addressBar.setText(currentWebpage);
mWebview = (WebView)findViewById(R.id.webview);
mWebview.getSettings().setJavaScriptEnabled(true); // enables javascript
mWebview.setWebViewClient(new WebViewClient());
System.out.println("Loading Webpage...");
mWebview.loadUrl(currentWebpage);
}
public void speakOut(String text) {
TextToSpeech tts = new TextToSpeech(this, this);
System.out.println("Speaking");
if(tts.isLanguageAvailable(Locale.ENGLISH) != -1){
tts.speak(text, TextToSpeech.QUEUE_FLUSH, null);
}
}
public int speakFull(String text){
switchToRead();
String[] sentences = text.split("\n|\\.(?!\\d)|(?<!\\d)\\."); // Regex that splits the body of text into the sentences of that body which are stored in a String array.
for(int i = 0; i < sentences.length; i++){
speakOut(sentences[i]);
if(i == sentences.length - 1){
return 1;
}
}
return 0;
}
public String getText(String webPage) throws ParseException, IOException{
HttpResponse response = null;
try {
HttpClient client = new DefaultHttpClient();
HttpGet request = new HttpGet();
request.setURI(new URI("http://someserver.net:8080/" + webPage));
response = client.execute(request);
} catch (URISyntaxException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
String responseBody = "No text found on webpage.";
int responseCode = response.getStatusLine().getStatusCode();
switch(responseCode) {
case 200:
HttpEntity entity = response.getEntity();
if(entity != null) {
responseBody = EntityUtils.toString(entity);
}
}
System.out.println("Returning Response..");
System.out.println(responseBody);
return responseBody;
}
@Override
public void onInit(int status) {
// TODO Auto-generated method stub
}
private class tts extends AsyncTask<String, Void, String>{//Async http request to get text
@Override
protected String doInBackground(String... arg0) {
try {
System.out.println("Running seperate thread for TTS.");
int complete = 0;
while(complete == 0){
System.out.println("Speaking full..");
complete = speakFull(getText(mWebview.getUrl()));
}
} catch (ParseException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
protected void onPostExecute(String result){
}
}
public void clickPlay(View v){
new tts().execute("");
}
public void clickGo(View v){
if(addressBar.getText() != null){
currentWebpage = addressBar.getText().toString();
System.out.println("Current webpage changed to: " + currentWebpage);
mWebview.loadUrl(currentWebpage);
}
}
public void clickPause(View v){
System.out.println("Clicked pause.");
}
@Override
public void onClick(DialogInterface dialog, int which) {
// TODO Auto-generated method stub
}
public void switchToRead(){// Switches to the reading view which displays the text that the tts engine reads off.
System.out.println("Swtiching view to Read.");
viewGroup.removeView(main);
viewGroup.addView(View.inflate(this, R.layout.read_out, null));
}
public void switchToMain(){
System.out.println("Switching view to Main.");
viewGroup.removeView(readOut);
viewGroup.addView(View.inflate(this, R.layout.activity_main, null));
}
}
此处还有我在启动应用时遇到的众多错误：
08-01 14:53:10.210: E/Trace(812): error opening trace file: No such file or directory (2)
08-01 14:53:10.600: D/AndroidRuntime(812): Shutting down VM
08-01 14:53:10.631: W/dalvikvm(812): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
08-01 14:53:10.660: E/AndroidRuntime(812): FATAL EXCEPTION: main
08-01 14:53:10.660: E/AndroidRuntime(812): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.webview/com.example.webview.MainActivity}: java.lang.NullPointerException
08-01 14:53:10.660: E/AndroidRuntime(812): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106)
08-01 14:53:10.660: E/AndroidRuntime(812): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
08-01 14:53:10.660: E/AndroidRuntime(812): at android.app.ActivityThread.access$600(ActivityThread.java:141)
08-01 14:53:10.660: E/AndroidRuntime(812): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
08-01 14:53:10.660: E/AndroidRuntime(812): at android.os.Handler.dispatchMessage(Handler.java:99)
08-01 14:53:10.660: E/AndroidRuntime(812): at android.os.Looper.loop(Looper.java:137)
08-01 14:53:10.660: E/AndroidRuntime(812): at android.app.ActivityThread.main(ActivityThread.java:5041)
08-01 14:53:10.660: E/AndroidRuntime(812): at java.lang.reflect.Method.invokeNative(Native Method)
08-01 14:53:10.660: E/AndroidRuntime(812): at java.lang.reflect.Method.invoke(Method.java:511)
08-01 14:53:10.660: E/AndroidRuntime(812): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
08-01 14:53:10.660: E/AndroidRuntime(812): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
08-01 14:53:10.660: E/AndroidRuntime(812): at dalvik.system.NativeStart.main(Native Method)
08-01 14:53:10.660: E/AndroidRuntime(812): Caused by: java.lang.NullPointerException
08-01 14:53:10.660: E/AndroidRuntime(812): at android.app.Activity.findViewById(Activity.java:1839)
08-01 14:53:10.660: E/AndroidRuntime(812): at com.example.webview.MainActivity.<init>(MainActivity.java:39)
08-01 14:53:10.660: E/AndroidRuntime(812): at java.lang.Class.newInstanceImpl(Native Method)
08-01 14:53:10.660: E/AndroidRuntime(812): at java.lang.Class.newInstance(Class.java:1319)
08-01 14:53:10.660: E/AndroidRuntime(812): at android.app.Instrumentation.newActivity(Instrumentation.java:1054)
08-01 14:53:10.660: E/AndroidRuntime(812): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097)
08-01 14:53:10.660: E/AndroidRuntime(812): ... 11 more
08-01 14:53:27.439: D/AndroidRuntime(860): Shutting down VM
08-01 14:53:27.439: W/dalvikvm(860): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
08-01 14:53:27.449: E/AndroidRuntime(860): FATAL EXCEPTION: main
08-01 14:53:27.449: E/AndroidRuntime(860): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.webview/com.example.webview.MainActivity}: java.lang.NullPointerException
08-01 14:53:27.449: E/AndroidRuntime(860): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106)
08-01 14:53:27.449: E/AndroidRuntime(860): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
08-01 14:53:27.449: E/AndroidRuntime(860): at android.app.ActivityThread.access$600(ActivityThread.java:141)
08-01 14:53:27.449: E/AndroidRuntime(860): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
08-01 14:53:27.449: E/AndroidRuntime(860): at android.os.Handler.dispatchMessage(Handler.java:99)
08-01 14:53:27.449: E/AndroidRuntime(860): at android.os.Looper.loop(Looper.java:137)
08-01 14:53:27.449: E/AndroidRuntime(860): at android.app.ActivityThread.main(ActivityThread.java:5041)
08-01 14:53:27.449: E/AndroidRuntime(860): at java.lang.reflect.Method.invokeNative(Native Method)
08-01 14:53:27.449: E/AndroidRuntime(860): at java.lang.reflect.Method.invoke(Method.java:511)
08-01 14:53:27.449: E/AndroidRuntime(860): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
08-01 14:53:27.449: E/AndroidRuntime(860): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
08-01 14:53:27.449: E/AndroidRuntime(860): at dalvik.system.NativeStart.main(Native Method)
08-01 14:53:27.449: E/AndroidRuntime(860): Caused by: java.lang.NullPointerException
08-01 14:53:27.449: E/AndroidRuntime(860): at android.app.Activity.findViewById(Activity.java:1839)
08-01 14:53:27.449: E/AndroidRuntime(860): at com.example.webview.MainActivity.<init>(MainActivity.java:39)
08-01 14:53:27.449: E/AndroidRuntime(860): at java.lang.Class.newInstanceImpl(Native Method)
08-01 14:53:27.449: E/AndroidRuntime(860): at java.lang.Class.newInstance(Class.java:1319)
08-01 14:53:27.449: E/AndroidRuntime(860): at android.app.Instrumentation.newActivity(Instrumentation.java:1054)
08-01 14:53:27.449: E/AndroidRuntime(860): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097)
08-01 14:53:27.449: E/AndroidRuntime(860): ... 11 more
答案 0 :(得分：4)
在onCreate
setContentView内移动视图初始化
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.mylayout);
LinearLayout viewGroup = (LinearLayout) findViewById(R.id.linearview);
...// rest of the code