我是adnroid的新手并且正在开发计算器应用程序。
我的应用程序没有错误但它不起作用。当我运行应用程序时，它说HesapMakinası已停止。
这是我的代码。变量是土耳其语。
package com.example.hesapmakinesi;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
public class MainActivity extends Activity {
/** Called when the activity is first created. */
double sayi1=0;
double sayi2=0;
String islem;
double sonuc=0;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button no0 = (Button)findViewById(R.id.button1);
Button no1 = (Button)findViewById(R.id.button2);
Button no2 = (Button)findViewById(R.id.button3);
Button no3 = (Button)findViewById(R.id.button4);
Button no4 = (Button)findViewById(R.id.button5);
Button no5 = (Button)findViewById(R.id.button6);
Button no6 = (Button)findViewById(R.id.button7);
Button no7 = (Button)findViewById(R.id.button8);
Button no8 = (Button)findViewById(R.id.button9);
Button no9 = (Button)findViewById(R.id.button10);
Button arti = (Button)findViewById(R.id.button11);
Button eksi = (Button)findViewById(R.id.button12);
Button carpi = (Button)findViewById(R.id.button14);
Button bolu = (Button)findViewById(R.id.button13);
Button esittir = (Button)findViewById(R.id.button15);
Button sifirla = (Button)findViewById(R.id.button16);
Button teksil = (Button)findViewById(R.id.button17);
final EditText islemekran = (EditText)findViewById(R.id.islemekran);
// Her Button ve Edittext için bir nesne tanımlandı ve
// findViewById fonksiyonuyla nesnelere bileşenler atandı.
//0-9 arası sayılar için tıklama olayları ve gerekli kodlar.
no0.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
islemekran.setText(islemekran.getText()+"0");
}
});
no1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
islemekran.setText(islemekran.getText()+"1");
}
});
no2.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
islemekran.setText(islemekran.getText()+"2");
}
});
no3.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
islemekran.setText(islemekran.getText()+"3");
}
});
no4.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
islemekran.setText(islemekran.getText()+"4");
}
});
no5.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
islemekran.setText(islemekran.getText()+"5");
}
});
no6.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
islemekran.setText(islemekran.getText()+"6");
}
});
no7.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
islemekran.setText(islemekran.getText()+"7");
}
});
no8.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
islemekran.setText(islemekran.getText()+"8");
}
});
no9.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
islemekran.setText(islemekran.getText()+"9");
}
});
// İşlemler için tıklama olayları ve gerekli kodlar
arti.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
try {
sayi1=Double.parseDouble(islemekran.getText().toString());
islemekran.setText("");
islem = "+";
} catch (Exception e) {
}
}
});
eksi.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(!(islemekran.getText().toString().equals("")))
{
sayi1=Double.parseDouble(islemekran.getText().toString());
islemekran.setText("");
islem = "-";
}
}
});
carpi.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(!(islemekran.getText().toString().equals("")))
{
sayi1=Double.parseDouble(islemekran.getText().toString());
islemekran.setText("");
islem = "x";
}
}
});
bolu.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(!(islemekran.getText().toString().equals("")))
{
sayi1=Double.parseDouble(islemekran.getText().toString());
islemekran.setText("");
islem = "/";
}
}
});
esittir.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
try {
sayi2=Double.parseDouble((islemekran.getText().toString()));
if(islem.equals("+"))
{
sonuc = sayi1+sayi2;
sayi1=0;
sayi2=0;
}else if(islem.equals("-"))
{
sonuc = sayi1-sayi2;
sayi1=0;
sayi2=0;
}else if(islem.equals("x"))
{
sonuc = sayi1*sayi2;
sayi1=0;
sayi2=0;
}
else if(islem.equals("/"))
{
sonuc = sayi1/sayi2;
sayi1=0;
sayi2=0;
}
islemekran.setText(Double.toString(sonuc));
} catch (Exception e) {
}
}
});
sifirla.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
try {
islemekran.setText("");
islem="";
sayi1=0;
sayi2=0;
} catch (Exception e) {
}
}
});
teksil.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
try {
if(!(islemekran.getText().toString().equals("")))
{
String kopyaekran = islemekran.getText().toString();
kopyaekran=kopyaekran.substring(0, kopyaekran.length()-1);
islemekran.setText(kopyaekran);
}else
{
islem="";
}
} catch (Exception e) {
}
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
布局
</EditText>
<Button
android:id="@+id/button2"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/button1"
android:layout_alignBottom="@+id/button1"
android:layout_centerHorizontal="true"
android:text="@string/no2" />
<Button
android:id="@+id/button3"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/button2"
android:layout_alignBottom="@+id/button2"
android:layout_alignParentRight="true"
android:layout_marginRight="18dp"
android:text="@string/no3" />
<Button
android:id="@+id/button6"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/button3"
android:layout_alignTop="@+id/button5"
android:text="@string/no6" />
<Button
android:id="@+id/button8"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignTop="@+id/button7"
android:layout_centerHorizontal="true"
android:text="@string/no8" />
<Button
android:id="@+id/button9"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/button6"
android:layout_alignTop="@+id/button8"
android:text="@string/no9" />
<Button
android:id="@+id/button12"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/button9"
android:layout_alignTop="@+id/button11"
android:text="@string/eksi" />
<Button
android:id="@+id/button14"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/button13"
android:layout_alignBottom="@+id/button13"
android:layout_alignLeft="@+id/button11"
android:text="@string/arti" />
<Button
android:id="@+id/button15"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/button12"
android:layout_alignTop="@+id/button14"
android:text="@string/carpi" />
<Button
android:id="@+id/button1"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@+id/editText1"
android:layout_marginLeft="14dp"
android:text="@string/no1" />
<Button
android:id="@+id/button17"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/button16"
android:layout_alignBottom="@+id/button16"
android:layout_alignLeft="@+id/button15"
android:text="@string/esittir" />
<Button
android:id="@+id/button11"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/button10"
android:layout_alignBottom="@+id/button10"
android:layout_alignLeft="@+id/button8"
android:text="@string/arti" />
<Button
android:id="@+id/button7"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/button4"
android:layout_below="@+id/button4"
android:text="@string/no7" />
<Button
android:id="@+id/button10"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/button7"
android:layout_below="@+id/button7"
android:text="@string/no0" />
<Button
android:id="@+id/button13"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/button10"
android:layout_below="@+id/button10"
android:text="@string/bolu" />
<Button
android:id="@+id/button16"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/button13"
android:layout_alignRight="@+id/button14"
android:layout_below="@+id/button14"
android:layout_marginTop="32dp"
android:textColor="#00FF00"
android:text="@string/sil" />
<Button
android:id="@+id/button4"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/button1"
android:layout_below="@+id/button1"
android:text="@string/no4"/>
<Button
android:id="@+id/button5"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/button8"
android:layout_alignLeft="@+id/button8"
android:text="@string/no5" />
</RelativeLayout>
Logcat更新
05-27 16:46:18.641: E/Trace(802): error opening trace file: No such file or directory (2)
05-27 16:46:19.451: D/AndroidRuntime(802): Shutting down VM
05-27 16:46:19.471: W/dalvikvm(802): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
05-27 16:46:19.511: E/AndroidRuntime(802): FATAL EXCEPTION: main
05-27 16:46:19.511: E/AndroidRuntime(802): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.hesapmakinesi/com.example.hesapmakinesi.MainActivity}: java.lang.NullPointerException
05-27 16:46:19.511: E/AndroidRuntime(802): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
05-27 16:46:19.511: E/AndroidRuntime(802): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
05-27 16:46:19.511: E/AndroidRuntime(802): at android.app.ActivityThread.access$600(ActivityThread.java:141)
05-27 16:46:19.511: E/AndroidRuntime(802): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
05-27 16:46:19.511: E/AndroidRuntime(802): at android.os.Handler.dispatchMessage(Handler.java:99)
05-27 16:46:19.511: E/AndroidRuntime(802): at android.os.Looper.loop(Looper.java:137)
05-27 16:46:19.511: E/AndroidRuntime(802): at android.app.ActivityThread.main(ActivityThread.java:5041)
05-27 16:46:19.511: E/AndroidRuntime(802): at java.lang.reflect.Method.invokeNative(Native Method)
05-27 16:46:19.511: E/AndroidRuntime(802): at java.lang.reflect.Method.invoke(Method.java:511)
05-27 16:46:19.511: E/AndroidRuntime(802): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
05-27 16:46:19.511: E/AndroidRuntime(802): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
05-27 16:46:19.511: E/AndroidRuntime(802): at dalvik.system.NativeStart.main(Native Method)
05-27 16:46:19.511: E/AndroidRuntime(802): Caused by: java.lang.NullPointerException
05-27 16:46:19.511: E/AndroidRuntime(802): at com.example.hesapmakinesi.MainActivity.onCreate(MainActivity.java:46)
05-27 16:46:19.511: E/AndroidRuntime(802): at android.app.Activity.performCreate(Activity.java:5104)
05-27 16:46:19.511: E/AndroidRuntime(802): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
05-27 16:46:19.511: E/AndroidRuntime(802): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
05-27 16:46:19.511: E/AndroidRuntime(802): ... 11 more
05-27 16:47:00.441: I/Process(802): Sending signal. PID: 802 SIG: 9
答案 0 :(得分：1)
您的活动无法找到ID为 no0 ， no1 的任何内容，依此类推，因为在您的XML文件中，他们有ID＆＃ 39; s button2 ， button3 等。因此，当您尝试将NullPointerException设置为按钮时OnClickListener。
所以不要这样：
Button no2 = (Button)findViewById(R.id.no2);
你需要这个：
Button no2 = (Button)findViewById(R.id.button2);
等等。