Java 单击按钮时自动选中复选框
我想在单击按钮时选中一个复选框。当我运行这段代码时,它给出了空指针异常 这是我的密码Java 单击按钮时自动选中复选框,java,android,xml,android-layout,Java,Android,Xml,Android Layout,我想在单击按钮时选中一个复选框。当我运行这段代码时,它给出了空指针异常 这是我的密码 CheckBox mCheckBoxRegular = (CheckBox) findViewById(R.id.checkBoxRegular); Button regular = (Button)findViewById(R.id.buttonRegular); regular.setOnClickListener(new OnClickListener() {
CheckBox mCheckBoxRegular = (CheckBox) findViewById(R.id.checkBoxRegular);
Button regular = (Button)findViewById(R.id.buttonRegular);
regular.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
mCheckBoxRegular.setChecked(true);
}
}
例外是
08-22 13:24:14.947: E/AndroidRuntime(31390): FATAL EXCEPTION: main
08-22 13:24:14.947: E/AndroidRuntime(31390): java.lang.NullPointerException
08-22 13:24:14.947: E/AndroidRuntime(31390): at com.example.amazingnumbersample.MainActivity$2$2.onClick(MainActivity.java:128)
08-22 13:24:14.947: E/AndroidRuntime(31390): at android.view.View.performClick(View.java:3534)
08-22 13:24:14.947: E/AndroidRuntime(31390): at android.view.View$PerformClick.run(View.java:14263)
08-22 13:24:14.947: E/AndroidRuntime(31390): at android.os.Handler.handleCallback(Handler.java:605)
08-22 13:24:14.947: E/AndroidRuntime(31390): at android.os.Handler.dispatchMessage(Handler.java:92)
08-22 13:24:14.947: E/AndroidRuntime(31390): at android.os.Looper.loop(Looper.java:137)
08-22 13:24:14.947: E/AndroidRuntime(31390): at android.app.ActivityThread.main(ActivityThread.java:4441)
08-22 13:24:14.947: E/AndroidRuntime(31390): at java.lang.reflect.Method.invokeNative(Native Method)
08-22 13:24:14.947: E/AndroidRuntime(31390): at java.lang.reflect.Method.invoke(Method.java:511)
08-22 13:24:14.947: E/AndroidRuntime(31390): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
08-22 13:24:14.947: E/AndroidRuntime(31390): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
08-22 13:24:14.947: E/AndroidRuntime(31390): at dalvik.system.NativeStart.main(Native Method)
请帮帮我。我已经尝试了你的代码并做了一些更改。它看起来像你想要的那样工作
public class MainActivity extends Activity {
CheckBox mCheckBoxRegular;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mCheckBoxRegular = (CheckBox) findViewById(R.id.checkBox1);
Button regular = (Button) findViewById(R.id.button1);
regular.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mCheckBoxRegular.setChecked(true);
}
});
}
}
我已经尝试了你的代码,并做了一些更改。它看起来像你想要的那样工作
public class MainActivity extends Activity {
CheckBox mCheckBoxRegular;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mCheckBoxRegular = (CheckBox) findViewById(R.id.checkBox1);
Button regular = (Button) findViewById(R.id.button1);
regular.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mCheckBoxRegular.setChecked(true);
}
});
}
}
试试这个
在setContentViewR.layout.activity之后
final CheckBox mCheckBoxRegular = (CheckBox) findViewById(R.id.checkBoxRegular);
Button regular = (Button)findViewById(R.id.buttonRegular);
regular.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
mCheckBoxRegular.setChecked(true);
}
});
试试这个
在setContentViewR.layout.activity之后
final CheckBox mCheckBoxRegular = (CheckBox) findViewById(R.id.checkBoxRegular);
Button regular = (Button)findViewById(R.id.buttonRegular);
regular.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
mCheckBoxRegular.setChecked(true);
}
});
哪一行给出了例外?在StackOverflow上已经提出了类似的问题。也许它有你想要的答案?添加最后的修饰语。就像最后一个复选框mCheckBoxRegular一样。并确保您使用的布局与给定id的复选框相同。哪一行给出了异常?在StackOverflow上已经提出了类似的问题。也许它有你想要的答案?添加最后的修饰语。就像最后一个复选框mCheckBoxRegular一样。并确保使用与给定id的复选框相同的布局。无法分配最终字段MainActivity.mCheckBoxRegular,因为我声明了复选框mCheckBoxRegular globaly最终字段MainActivity.mCheckBoxRegular,因为我声明了复选框mCheckBoxRegular globaly