Android运行时错误
我是android应用程序的初学者。你能帮我解决这个问题吗。我已经包括了logcat入门和活动类 日志：Android运行时错误,android,button,runtime-error,Android,Button,Runtime Error,我是android应用程序的初学者。你能帮我解决这个问题吗。我已经包括了logcat入门和活动类 日志： 11-07 12:46:28.245: D/AndroidRuntime(579): Shutting down VM 11-07 12:46:28.245: W/dalvikvm(579): threadid=1: thread exiting with uncaught exception (group=0x40015560) 11-07 12:46:28.285: E/AndroidR
11-07 12:46:28.245: D/AndroidRuntime(579): Shutting down VM
11-07 12:46:28.245: W/dalvikvm(579): threadid=1: thread exiting with uncaught exception (group=0x40015560)
11-07 12:46:28.285: E/AndroidRuntime(579): FATAL EXCEPTION: main
11-07 12:46:28.285: E/AndroidRuntime(579): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.trial.login/com.trial.login.Login1Activity}: java.lang.NullPointerException
11-07 12:46:28.285: E/AndroidRuntime(579): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
11-07 12:46:28.285: E/AndroidRuntime(579): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
11-07 12:46:28.285: E/AndroidRuntime(579): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
11-07 12:46:28.285: E/AndroidRuntime(579): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
11-07 12:46:28.285: E/AndroidRuntime(579): at android.os.Handler.dispatchMessage(Handler.java:99)
11-07 12:46:28.285: E/AndroidRuntime(579): at android.os.Looper.loop(Looper.java:123)
11-07 12:46:28.285: E/AndroidRuntime(579): at android.app.ActivityThread.main(ActivityThread.java:3683)
11-07 12:46:28.285: E/AndroidRuntime(579): at java.lang.reflect.Method.invokeNative(Native Method)
11-07 12:46:28.285: E/AndroidRuntime(579): at java.lang.reflect.Method.invoke(Method.java:507)
11-07 12:46:28.285: E/AndroidRuntime(579): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
11-07 12:46:28.285: E/AndroidRuntime(579): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
11-07 12:46:28.285: E/AndroidRuntime(579): at dalvik.system.NativeStart.main(Native Method)
11-07 12:46:28.285: E/AndroidRuntime(579): Caused by: java.lang.NullPointerException
11-07 12:46:28.285: E/AndroidRuntime(579): at com.trial.login.Login1Activity.onCreate(Login1Activity.java:28)
11-07 12:46:28.285: E/AndroidRuntime(579): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
11-07 12:46:28.285: E/AndroidRuntime(579): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
11-07 12:46:28.285: E/AndroidRuntime(579): ... 11 more
package com.trial.login;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class Login1Activity extends Activity {
TextView username, password;
EditText user_edit, pwd_edit;
Button login, cancel;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
login = (Button) findViewById(R.id.bt1);
cancel = (Button) findViewById(R.id.bt2);
username = (TextView) findViewById(R.id.tv1);
password = (TextView) findViewById(R.id.tv2);
user_edit = (EditText) findViewById(R.id.txtUname);
pwd_edit = (EditText) findViewById(R.id.txtPwd);
login.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
display();
}
});
}
cancel.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
user_edit.clearComposingText();
pwd_edit.clearComposingText();
}
});
public void display(){
String user_temp, pwd_temp;
user_temp = user_edit.getText().toString();
pwd_temp = pwd_edit.getText().toString();
username.setText(user_temp);
password.setText(pwd_temp);
}
}
我不确定它是否能解决您的问题，但不应该取消。setOnClickListener是否在onCreate中？我必须承认，我不太熟悉Java如何初始化对象，但可能是在cancel指向任何对象之前执行了这段代码。我不确定它是否能解决您的问题，但不应该取消。setOnClickListener是否在onCreate中？我必须承认，我不太熟悉Java如何初始化对象，但可能是在cancel指向任何对象之前执行了这段代码。尝试以下方法：
package com.trial.login;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class Login1Activity extends Activity {
TextView username, password;
EditText user_edit, pwd_edit;
Button login, cancel;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
login = (Button) findViewById(R.id.bt1);
cancel = (Button) findViewById(R.id.bt2);
username = (TextView) findViewById(R.id.tv1);
password = (TextView) findViewById(R.id.tv2);
user_edit = (EditText) findViewById(R.id.txtUname);
pwd_edit = (EditText) findViewById(R.id.txtPwd);
login.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
display();
}
});
cancel.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
user_edit.clearComposingText();
pwd_edit.clearComposingText();
}
});
}
public void display(){
String user_temp, pwd_temp;
user_temp = user_edit.getText().toString();
pwd_temp = pwd_edit.getText().toString();
username.setText(user_temp);
password.setText(pwd_temp);
}
}
package com.trial.login;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class Login1Activity extends Activity {
TextView username, password;
EditText user_edit, pwd_edit;
Button login, cancel;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
login = (Button) findViewById(R.id.bt1);
cancel = (Button) findViewById(R.id.bt2);
username = (TextView) findViewById(R.id.tv1);
password = (TextView) findViewById(R.id.tv2);
user_edit = (EditText) findViewById(R.id.txtUname);
pwd_edit = (EditText) findViewById(R.id.txtPwd);
login.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
display();
}
});
cancel.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
user_edit.clearComposingText();
pwd_edit.clearComposingText();
}
});
}
public void display(){
String user_temp, pwd_temp;
user_temp = user_edit.getText().toString();
pwd_temp = pwd_edit.getText().toString();
username.setText(user_temp);
password.setText(pwd_temp);
}
}
检查代码中使用的所有视图是否存在于main.xml中。 还要检查您在代码中编写的所有视图ID是否与main.xml中的ID相同
*将onCreate方法结束括号放在cancel.setOnClickListener之后，检查代码中使用的所有视图是否存在于main.xml中。 还要检查您在代码中编写的所有视图ID是否与main.xml中的ID相同
*将onCreate方法结束括号放在cancel.setOnClickListener之后是否可以发布main.xml文件？是否可以发布main.xml文件？