java.lang.RuntimeException:无法启动活动
我的应用程序在启动时总是崩溃。这是Android监视器上的错误。以下代码来自我的片段,应该从应用程序的开头开始:java.lang.RuntimeException:无法启动活动,java,android,android-fragments,nullpointerexception,runtime-error,Java,Android,Android Fragments,Nullpointerexception,Runtime Error,我的应用程序在启动时总是崩溃。这是Android监视器上的错误。以下代码来自我的片段,应该从应用程序的开头开始: 01-30 23:42:55.281 5767-5767/silverbeach.meintieralter E/AndroidRuntime: FATAL EXCEPTION: main Process: silverbeach.mein
01-30 23:42:55.281 5767-5767/silverbeach.meintieralter E/AndroidRuntime: FATAL EXCEPTION: main
Process: silverbeach.meintieralter, PID: 5767
java.lang.RuntimeException: Unable to start activity ComponentInfo{silverbeach.meintieralter/silverbeach.meintieralter.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3254)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3350)
at android.app.ActivityThread.access$1100(ActivityThread.java:222)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1795)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7229)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at silverbeach.meintieralter.FragmentOne.onCreate(FragmentOne.java:36)
at android.app.Fragment.performCreate(Fragment.java:2242)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:947)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1163)
at android.app.BackStackRecord.run(BackStackRecord.java:793)
at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1552)
at android.app.FragmentController.execPendingActions(FragmentController.java:325)
at android.app.Activity.performStart(Activity.java:6914)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3217)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3350)
at android.app.ActivityThread.access$1100(ActivityThread.java:222)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1795)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7229)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
01-30 23:42:55.401 5767-5767/silverbeach.meintieralter I/Process: Sending signal. PID: 5767 SIG: 9
代码
package silverbeach.meintieralter;
import android.app.Fragment;
import android.content.Context;
import android.os.Bundle;
import android.os.Vibrator;
import android.support.annotation.Nullable;
import android.support.design.widget.Snackbar;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;
import android.view.View.OnClickListener;
import static android.content.Context.VIBRATOR_SERVICE;
public class FragmentOne extends Fragment {
private TextView out;
private EditText alter;
private Spinner s;
private Button button;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String text = s.getSelectedItem().toString();
int newage = 404;
double doublenewage = 4.04;
double doubleage;
int intage;
doubleage = Double.parseDouble(alter.getText().toString());
intage = (int) doubleage;
switch (text) {
case "Pferd": {
doublenewage = intage / 3.1;
long longpferdage = Math.round(doublenewage);
newage = (int) longpferdage;
if (newage < 31)
out.setText("Du bist ein " + Integer.toString(newage) + " Jahre altes Pferd");
else
out.setText("Du bist höchstwahrscheinlich schon tot, aber theoretisch wärst du ein " + newage + "-Jähriges Pferd.");
}break;
case "Hund": {
newage = intage / 7;
if (newage < 15)
out.setText("Du bist ein " + Integer.toString(newage) + " Jahre alter Hund.");
else
out.setText("Du bist höchstwahrscheinlich schon tot, aber theoretisch wärst du ein " + newage + "-Jähriger Hund.");
}break;
case "Meerschweinchen": {
newage = intage / 12;
if (newage < 8)
//out.setText("Du bist ein " + Integer.toString(newage) + " Jahre altes Meerie.");
out.setText( "Du bist ein "+Integer.toString(newage)+" Jahre altes Meerie.");
else
out.setText("Du bist höchstwahrscheinlich schon tot, aber theoretisch wärst du ein " + newage + "-Jähriges Meerie.");
}break;
}
}
});
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View layout = inflater.inflate(R.layout.fragment_one, null);
out = (TextView) layout.findViewById(R.id.out);
alter = (EditText) layout.findViewById(R.id.altereingabe);
s = (Spinner) layout.findViewById(R.id.spinner);
button = (Button) layout.findViewById(R.id.button);
// tvText1 = (TextView) layout.findViewById(R.id.tvFragmentOne);
return layout;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
//tvText1.setText("Ok View 1 wurde geändert.");
}
package silverbeach.meintierlater;
导入android.app.Fragment;
导入android.content.Context;
导入android.os.Bundle;
导入android.os.可控震源;
导入android.support.annotation.Nullable;
导入android.support.design.widget.Snackbar;
导入android.view.LayoutInflater;
导入android.view.view;
导入android.view.ViewGroup;
导入android.widget.Button;
导入android.widget.EditText;
导入android.widget.Spinner;
导入android.widget.TextView;
导入android.view.view.OnClickListener;
导入静态android.content.Context.u服务;
公共类FragmentOne扩展了Fragment{
私有文本视图输出;
私人编辑文本修改;
私人纺纱机;
私人按钮;
@凌驾
创建时的公共void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setOnClickListener(新视图.OnClickListener(){
@凌驾
公共void onClick(视图v){
String text=s.getSelectedItem().toString();
int newage=404;
双新年龄=4.04;
双倍年龄;
int intage;
doubleage=Double.parseDouble(alter.getText().toString());
摄入量=(整数)双倍年龄;
开关(文本){
案例“Pferd”:{
doublenewage=intage/3.1;
long longpferdage=Math.round(doublenewage);
newage=(int)longpferdage;
如果(新年龄<31)
out.setText(“Du bist ein”+Integer.toString(newage)+“Jahre altes Pferd”);
其他的
out.setText(“Du bist höchstwahrscheinlich schon tot,aber theoretisch wärst Du ein”+newage+“-Jähriges Pferd”);
}中断;
“洪德”案:{
newage=intage/7;
如果(新年龄<15岁)
out.setText(“Du bist ein”+Integer.toString(newage)+“Jahre alter Hund”);
其他的
out.setText(“Du bist höchstwahrscheinlich schon tot,aber theoretisch wärst Du ein”+“newage+”-Jähriger Hund.”);
}中断;
案例“Meerschweinchen”:{
新年龄=摄入量/12;
如果(新年龄<8)
//out.setText(“Du bist ein”+Integer.toString(newage)+“Jahre altes Meerie”);
out.setText(“Du bist ein”+Integer.toString(newage)+“Jahre altes Meerie”);
其他的
out.setText(“Du bist höchstwahrscheinlich schon tot,aber theoretisch wärst Du ein”+“newage+”-Jähriges Meerie”);
}中断;
}
}
});
}
@可空
@凌驾
CreateView上的公共视图(布局、充气机、视图组容器、捆绑包保存状态){
视图布局=充气机。充气(R.layout.fragment\u one,null);
out=(TextView)layout.findViewById(R.id.out);
alter=(EditText)layout.findViewById(R.id.altereingabe);
s=(微调器)layout.findviewbyd(R.id.Spinner);
按钮=(按钮)布局。findViewById(R.id.button);
//tvText1=(TextView)layout.findViewById(R.id.tvFragmentOne);
返回布局;
}
@凌驾
已创建ActivityState上的公共无效(Bundle savedInstanceState){
super.onActivityCreated(savedInstanceState);
//tvText1.setText(“Ok View 1 wurde geändert.”);
}
}
按钮
在该点为空。在设置侦听器之前,需要使用button=(button)findViewById(R.id.)
。onCreate
在onCreateView
之前调用,因此在将侦听器分配给视图时,其仍然为空
因此,我建议将
按钮.setOnClickListener
移动到onCreateView()
。方法这可能会有所帮助:我的主要活动我已经像在另一篇文章中一样启动了片段。你不能在onCreate in fragment中这样做,你必须使用onCreateView参数中的充气器。你需要充气布局,以便能够进行像findViewById这样的UI操作。事实上,在您的案例中,您甚至不需要片段中的onCreate方法,只需将所有内容移动到onCreateView即可。这很正确,但在扩展它之前,您也不能使用它。因此,如果要在onCreateView中设置变量,还需要在那里设置侦听器。为什么这篇文章得到-1?我是Stackoverflow的新员工。这是一个错误类型的问题吗?@Georq,因为它实际上在stacktrace中给了你答案,对这里的大多数人来说,这是一个微不足道的问题,但我知道你的感觉,我也是新来的,如果你希望有人做出回应,你需要在这个问题上付出一些努力。