Java Android程序上的主要错误_Java_Android_Android Studio

Java Android程序上的主要错误

java android android-studio

Java Android程序上的主要错误,java,android,android-studio,Java,Android,Android Studio,我尝试运行程序时出错。。。不知道发生了什么，请帮助我，我对java真的很陌生。这是一个简单的计算器gui，当按下按钮时，我试图让文本显示在文本视图中 package com.ab.calculator; import android.support.v7.app.ActionBarActivity; import android.os.Bundle; import android.view.Menu; import android.view.MenuItem; import andro

我尝试运行程序时出错。。。不知道发生了什么，请帮助我，我对java真的很陌生。这是一个简单的计算器gui，当按下按钮时，我试图让文本显示在文本视图中

    package com.ab.calculator;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;


public class Calc1 extends ActionBarActivity {
    Button btn7;
    TextView txt = (TextView)findViewById(R.id.textView);
    int x,y,z;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_calc1);


        // btn7.setOnClickListener(new OnClickListener() {

    }
    void updatescore(){
        TextView text = (TextView) findViewById(R.id.textView);
        text.setText(x );
    }

    public void onToggleClicked(View view) {
        btn7 = (Button)findViewById(R.id.button2);
        boolean on = ((Button) view).performClick();

        if (on) {
            x = 7;
        }
        updatescore();
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_calc1, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

这是日志

    10-22 17:21:47.160 13640-13640/? D/dalvikvm: Late-enabling CheckJNI
    10-22 17:21:47.261 13640-13640/com.ab.calculator D/AndroidRuntime: Shutting down VM
    10-22 17:21:47.261 13640-13640/com.ab.calculator W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0x416cc930)
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime: FATAL EXCEPTION: main
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime: java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.ab.calculator/com.ab.calculator.Calc1}: java.lang.NullPointerException
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106)
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at android.app.ActivityThread.access$600(ActivityThread.java:141)
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:99)
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:137)
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5041)
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method)
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:511)
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at dalvik.system.NativeStart.main(Native Method)
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:  Caused by: java.lang.NullPointerException
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at android.app.Activity.findViewById(Activity.java:1839)
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at com.ab.calculator.Calc1.<init>(Calc1.java:16)
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at java.lang.Class.newInstanceImpl(Native Method)
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at java.lang.Class.newInstance(Class.java:1319)
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at android.app.Instrumentation.newActivity(Instrumentation.java:1054)
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097)
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at android.app.ActivityThread.access$600(ActivityThread.java:141) 
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:99) 
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:137) 
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5041) 
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method) 
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:511) 
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
    10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:     at dalvik.system.NativeStart.main(Native Method) 
    10-22 17:22:37.457 13640-13640/? I/Process: Sending signal. PID: 13640 SIG: 9

10-22 17:21:47.160 13640-13640/？D/dalvikvm：延迟启用CheckJNI
10-22 17:21:47.26113640-13640/com.ab.calculator D/AndroidRuntime:关闭虚拟机
10-22 17:21:47.261 13640-13640/com.ab.calculator W/dalvikvm:threadid=1:线程以未捕获异常退出（组=0x416cc930）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:致命异常：main
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:java.lang.RuntimeException:无法实例化活动组件信息{com.ab.calculator/com.ab.calculator.Calc1}:java.lang.NullPointerException
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:at-android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2106）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:at-android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2230）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:android.app.ActivityThread.access$600（ActivityThread.java:141）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:at-android.app.ActivityThread$H.handleMessage（ActivityThread.java:1234）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:at-android.os.Handler.dispatchMessage（Handler.java:99）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:at-android.os.Looper.loop（Looper.java:137）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:at-android.app.ActivityThread.main（ActivityThread.java:5041）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:at java.lang.reflect.Method.invokenactive（本机方法）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:at java.lang.reflect.Method.invoke（Method.java:511）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run（ZygoteInit.java:793）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:com.android.internal.os.ZygoteInit.main（ZygoteInit.java:560）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:dalvik.system.NativeStart.main（本机方法）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:由以下原因引起：java.lang.NullPointerException
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:at-android.app.Activity.findViewById（Activity.java:1839）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:com.ab.calculator.Calc1.（Calc1.java:16）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:at java.lang.Class.newInstanceImpl（本机方法）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:at java.lang.Class.newInstance（Class.java:1319）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:at-android.app.Instrumentation.newActivity（Instrumentation.java:1054）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:at-android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2097）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:at-android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2230）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:android.app.ActivityThread.access$600（ActivityThread.java:141）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:at-android.app.ActivityThread$H.handleMessage（ActivityThread.java:1234）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:at-android.os.Handler.dispatchMessage（Handler.java:99）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:at-android.os.Looper.loop（Looper.java:137）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:at-android.app.ActivityThread.main（ActivityThread.java:5041）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:at java.lang.reflect.Method.invokenactive（本机方法）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:at java.lang.reflect.Method.invoke（Method.java:511）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run（ZygoteInit.java:793）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:com.android.internal.os.ZygoteInit.main（ZygoteInit.java:560）
10-22 17:21:47.269 13640-13640/com.ab.calculator E/AndroidRuntime:dalvik.system.NativeStart.main（本机方法）
10-22 17:22:37.457 13640-13640/? I/进程：发送信号。PID:13640信号：9

您必须将TextView分配移动到onCreate（）方法。所以安卓知道在设置setContentView（…）之后应该膨胀哪个布局

编辑：我看到你每次需要文本视图时都会通过findViewById（…）获取它。如果您只在onCreate中分配它，然后将此引用用于TextView，它的功能将更加强大。

It；它不是主要的，只是由java.lang.NullPointerException引起的。发布一些代码以获得有用的答案。错误指向哪一行？请参阅：

protected void onCreate(Bundle savedInstanceState){

    super(...);
    setContentView(...);
    txt = (TextView)findViewById(R.id.textView);

}