我在两个活动之间传递两个字符串，由于某种原因，当我尝试接受字符串时它会崩溃。我觉得，我错过了一些重要的东西，却无法找到任何我错过的代码。 Google取得了很少甚至没有结果，我真的很恼火，因为这似乎是一项非常基本的任务。
任何帮助，将不胜感激:)
logcat的：
03-25 04:23:03.476: E/AndroidRuntime(1174): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.gta5news.bananaphone/com.gta5news.bananaphone.ChatService}: java.lang.NullPointerException
03-25 04:23:03.476: E/AndroidRuntime(1174): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
03-25 04:23:03.476: E/AndroidRuntime(1174): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
03-25 04:23:03.476: E/AndroidRuntime(1174): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
03-25 04:23:03.476: E/AndroidRuntime(1174): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
03-25 04:23:03.476: E/AndroidRuntime(1174): at android.os.Handler.dispatchMessage(Handler.java:99)
03-25 04:23:03.476: E/AndroidRuntime(1174): at android.os.Looper.loop(Looper.java:123)
03-25 04:23:03.476: E/AndroidRuntime(1174): at android.app.ActivityThread.main(ActivityThread.java:4627)
03-25 04:23:03.476: E/AndroidRuntime(1174): at java.lang.reflect.Method.invokeNative(Native Method)
03-25 04:23:03.476: E/AndroidRuntime(1174): at java.lang.reflect.Method.invoke(Method.java:521)
03-25 04:23:03.476: E/AndroidRuntime(1174): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
03-25 04:23:03.476: E/AndroidRuntime(1174): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
03-25 04:23:03.476: E/AndroidRuntime(1174): at dalvik.system.NativeStart.main(Native Method)
03-25 04:23:03.476: E/AndroidRuntime(1174): Caused by: java.lang.NullPointerException
03-25 04:23:03.476: E/AndroidRuntime(1174): at com.gta5news.bananaphone.ChatService.GetLogInData(ChatService.java:76)
03-25 04:23:03.476: E/AndroidRuntime(1174): at com.gta5news.bananaphone.ChatService.onCreate(ChatService.java:47)
03-25 04:23:03.476: E/AndroidRuntime(1174): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
03-25 04:23:03.476: E/AndroidRuntime(1174): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
03-25 04:23:03.476: E/AndroidRuntime(1174): ... 11 more
代码（第二项活动，即崩溃）
public class ChatService extends ListActivity {
/** Called when the activity is first created. */
BufferedReader in = null;
String data = null;
List headlines;
List links;
String GotPass = null;
String GotUname = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
GetLogInData();
try {
ContactsandIm();
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (URISyntaxException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
CheckLogin();
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
private void GetLogInData() {
// TODO Auto-generated method stub
Bundle gotData = getIntent().getExtras();
GotPass = gotData.getString("key!");
GotUname = gotData.getString("key!!");
}
private void CheckLogin() throws UnsupportedEncodingException {
}
public void ContactsandIm() throws URISyntaxException,
ClientProtocolException, IOException {
headlines = new ArrayList();
// TODO Auto-generated method stub
BufferedReader in = null;
String data = null;
HttpClient get = new DefaultHttpClient();
URI website = new URI("http://www.gta5news.com/test.php");
HttpGet webget = new HttpGet();
webget.setURI(website);
HttpResponse response = get.execute(webget);
Log.w("HttpPost", "Execute HTTP Post Request");
in = new BufferedReader(new InputStreamReader(response.getEntity()
.getContent()));
StringBuffer sb = new StringBuffer("");
String l ="";
String nl ="";
while ((l =in.readLine()) !=null) {
sb.append(l + nl);
}
in.close();
data = sb.toString();
if(data.contains("null"));
ListView lv = getListView();
lv.setTextFilterEnabled(true);
headlines.add(data);
ArrayAdapter adapter = new ArrayAdapter(this,
android.R.layout.simple_list_item_1, headlines);
setListAdapter(adapter);
}
// end bracket for "ContactsandIm"
}
第1次活动
public class LogIn extends Activity implements OnClickListener {
Button ok, back, exit;
TextView result;
EditText pword;
EditText uname;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// Login button clicked
ok = (Button) findViewById(R.id.btn_login);
ok.setOnClickListener(this);
result = (TextView) findViewById(R.id.lbl_result);
}
//create bracket.
public void postLoginData() {
// Create a new HttpClient and Post Header
HttpClient httpclient = new DefaultHttpClient();
/* login.php returns true if username and password is equal to saranga */
HttpPost httppost = new HttpPost("http://gta5news.com/login.php");
try {
// Add user name and password
uname = (EditText) findViewById(R.id.txt_username);
String username = uname.getText().toString();
pword = (EditText) findViewById(R.id.txt_password);
String password = pword.getText().toString();
Bundle basket = new Bundle();
basket.putString("key!", password);
basket.putString("key!!", username);
Intent a = new Intent(LogIn.this, ChatService.class );
a.putExtras(basket);
startActivity(a);
List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(2);
nameValuePairs.add(new BasicNameValuePair("username", username));
nameValuePairs.add(new BasicNameValuePair("password", password));
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
// Execute HTTP Post Request
Log.w("HttpPost", "Execute HTTP Post Request");
HttpResponse response = httpclient.execute(httppost);
String str = inputStreamToString(response.getEntity().getContent())
.toString();
Log.w("HttpPost", str);
if (str.toString().equalsIgnoreCase("true")) {
Log.w("HttpPost", "TRUE");
result.setText("Login successful");
try {Thread.sleep(250);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Intent login = new Intent(LogIn.this, ChatService.class);
startActivity(login);
} else {
Log.w("HttpPost", "FALSE");
result.setText(str);
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
private StringBuilder inputStreamToString(InputStream is) {
String line = "";
StringBuilder total = new StringBuilder();
// Wrap a BufferedReader around the InputStream
BufferedReader rd = new BufferedReader(new InputStreamReader(is));
// Read response until the end
try {
while ((line = rd.readLine()) != null) {
total.append(line);
}
} catch (IOException e) {
e.printStackTrace();
}
// Return full string
return total;
}
public void onClick(View view) {
if (view == ok) {
postLoginData();
InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
imm.hideSoftInputFromWindow(pword.getWindowToken(), 0);
}
// Click end
}
// if statement
}
// class ends here
答案 0 :(得分：2)
检查null：
Bundle gotData = getIntent().getExtras();
if(gotData != null)
{
GotPass = gotData.getString("key!");
GotUname = gotData.getString("key!!");
}
答案 1 :(得分：0)
in.close();
data = sb.toString();
if(data.contains("null"));
ListView lv = getListView();
lv.setTextFilterEnabled(true);
为什么这里引号为空？如果你正在寻找字符串“null”，这是一回事，但contains（）如果引用空字符串则抛出nullpointerexception。
此外，看起来你的if语句末尾有一个不必要的分号。
答案 2 :(得分：0)
确保您的第二个活动类已添加到您的应用清单文件中。 如果它已添加到您的清单文件中，则调用 -
startActivity(yourSecondIntentActivity);
finish();
玩得开心......