Java NullPointerException，是什么导致了我的错误？

Logcat在Records.java中的第42行返回一个nullPointerException。第42行显示daily_record.setTextDaily_record_选项；你们能浏览一下这个代码吗？我已经试着解决这个问题好几个小时了，但我所做的一切都无济于事。谢谢 Records.java

和布局文件： personal_records.xml

第43行显示：daily_record.setTextDaily_record_选项； 现在是43号线，因为我把一些东西移到了上面。但是抛出错误的区域在同一区域内/周围

MainActivity.java

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你能不能给我一些关于如何使ResetVariableTimer更好的想法？我想做的是在新的一天/一周到来时重置每日和每周计数器。我想这应该是一个后台服务，但我不知道该怎么做

您试图在不设置活动内容的情况下获取文本视图

将这些行放在setContentViewR.layout.personal_记录之后

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另外，您不应该在setText中使用integer；它有完全不同的含义。如果这样做，它将查找具有该整数值的资源。

您正在尝试获取TextView，而不设置活动中的内容

将这些行放在setContentViewR.layout.personal_记录之后

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另外，您不应该在setText中使用integer；它有完全不同的含义。如果这样做，它将查找具有该整数值的资源。

在引用视图中的任何元素之前，首先需要膨胀视图。当你有这两行代码时

TextView daily_record = (TextView) findViewById(R.id.daily_textview);
TextView weekly_record = (TextView) findViewById(R.id.weekly_textview);

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您的视图仍然为null，因此出现null指针异常。在引用任何元素之前，应首先调用setContentViewR.layout.myView。

在引用任何元素之前，首先需要膨胀视图。当你有这两行代码时

TextView daily_record = (TextView) findViewById(R.id.daily_textview);
TextView weekly_record = (TextView) findViewById(R.id.weekly_textview);

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您的视图仍然为null，因此出现null指针异常。在引用任何元素之前，您应该首先调用setContentViewR.layout.myView。

我刚刚调用了它，但仍然得到nullPointerException。您需要移动super.onCreatesavedInstanceState；setContentViewR.layout.personal_记录；在@Override public void onCreateBundle savedInstanceState之后{您能告诉我第42行对应的是什么吗？您能发布堆栈跟踪吗？我刚发布了，但仍然收到nullPointerException。您需要将super.onCreatesavedInstanceState；setContentViewR.layout.personal_records；移动到@Override public void onCreateBundle SavedinnstanceState之后{你能告诉我42行对应的是什么吗？你能发布堆栈跟踪吗？尝试更改line daily_record.setTextDaily_record_Option；使用daily_record.setTextDaily_record_Option+；@Rohit5k2不，这不起作用。你正在扩展MainActivity；可能是出了什么问题。这个类似乎没有任何错误，除了你不应该像您现在这样在setText方法中使用integer。在setText中使用integer具有完全不同的含义。我删除了extends MainActivity，并且到处都有错误。因此，为了解决这个问题，我显然按了ALT+ENTER以查看Android Studio的建议，但这没有帮助。在我的另一个活动中，我在setText a中使用了int它工作得很好。所以我完全不知道还有什么可以尝试。@Rohit5k2您认为问题可能源于这样一个事实，即当用户单击右上角名为“您的记录”的ActionBar项时Records.java活动启动了？这是一个片段吗？尝试更改line daily_record.SettexDaily_Record_Option；使用daily_record.setTextDaily_record_Option+；@Rohit5k2不，这不起作用。您正在扩展MainActivity；可能有问题。这个类似乎没有任何错误，只是您不应该像现在这样在setText方法中使用integer。在setText中使用integer有完全不同的含义。我删除了它nActivity和到处都有错误。因此，为了解决这个问题，我显然按下ALT+ENTER来查看Android Studio的建议，但这没有任何帮助。在我的另一个活动中，我在setText中使用了int，它工作得很好。所以我完全不知道还有什么可以尝试。@Rohit5k2您认为问题可能来自fa吗当用户单击右上角名为“您的记录”的ActionBar项时，Records.java活动是否启动？这是一个片段吗？

java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2305)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2359)
at android.app.ActivityThread.access$700(ActivityThread.java:165)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1326)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5455)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1187)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at haveabeer.two.padc.haveabeer.Records.onCreate(Records.java:43)
//Here ^^^
at android.app.Activity.performCreate(Activity.java:5372)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2267)

import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;


import android.view.Menu;
import android.view.MenuItem;
import android.view.View;

import android.widget.ImageButton;

import android.widget.TextView;
import android.widget.Toast;

import java.util.Calendar;


public class MainActivity extends ActionBarActivity {
public int counter = 0;
public int counter_weekly = 0;
Calendar daily_calender = Calendar.getInstance();
int hour = daily_calender.get(Calendar.HOUR);
int second = daily_calender.get(Calendar.SECOND);
int minute = daily_calender.get(Calendar.MINUTE);
int day = daily_calender.get(Calendar.DAY_OF_WEEK);
public boolean isSavedDaily = true;
public boolean isSavedWeekly = false;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    ImageButton beer = (ImageButton) findViewById(R.id.imageButton);
    SharedPreferences sharedPrefs = getSharedPreferences("Data",Context.MODE_PRIVATE);
    counter = sharedPrefs.getInt("daily", counter);
    counter_weekly = sharedPrefs.getInt("weekly", counter_weekly);
    TextView beer_count_onLoad = (TextView) findViewById(R.id.textView);
    beer_count_onLoad.setText(getResources().getString(R.string.beerCount) + "" + counter);
    TextView beer_week_count_onLoad = (TextView) findViewById(R.id.textView2);
    beer_week_count_onLoad.setText(getResources().getString(R.string.beerWeek) + "" +     counter_weekly);
    final TextView beer_count = (TextView) findViewById(R.id.textView);
    final TextView beer_week = (TextView) findViewById(R.id.textView2);


    beer.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            counter++;
            counter_weekly++;
            beer_count.setText(getResources().getString(R.string.beerCount) + "" + counter );
            beer_week.setText(getResources().getString(R.string.beerWeek) + "" + counter_weekly );


        }
    });

    ResetVariablesTimers();


}


private void ResetVariablesTimers() {
    SharedPreferences sharedPrefs = getSharedPreferences("Data",Context.MODE_PRIVATE);
    SharedPreferences.Editor editor = sharedPrefs.edit();
    if(hour == 0 && second == 0 && minute == 0 ){
        TextView reset_notification = (TextView)findViewById(R.id.textView3);
        reset_notification.setText("Daily was reset to 0, was at 400");
        editor.putInt("daily", counter);

        editor.commit();
        isSavedDaily=true;

        ResetVariables();





    }else{
        Toast.makeText(this, "Not time of the day yet", Toast.LENGTH_LONG).show();
        isSavedDaily=true;

        if(day == 2 && second == 0 && minute == 0 && hour == 0 ){
            TextView reset_notification_weekly = (TextView) findViewById(R.id.textView4);
            reset_notification_weekly.setText("Weekly was reset to 0, was at 400");
            editor.putInt("weekly", counter_weekly);
            editor.commit();
            isSavedWeekly=true;
            ResetVariables();
        }else{
            Toast.makeText(this, "Not time of the month yet", Toast.LENGTH_LONG).show();
            isSavedWeekly=false;
        }


    }}

public void ResetVariables() {
    if(Records.daily_recieved = true){
        counter = 0;
    }
    if(Records.weekly_recieved = true){
        counter_weekly = 0;
    }


}


@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_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    SharedPreferences sharedPrefs = getSharedPreferences("Data", Context.MODE_PRIVATE);
    SharedPreferences.Editor editor = sharedPrefs.edit();
    editor.putInt("daily", counter);
    editor.putInt("weekly", counter_weekly);
    editor.commit();
    // 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;
    }else if (id == R.id.Personal_Records && isSavedDaily){

        Intent records_intent = new Intent(this, Records.class);
        startActivity(records_intent);

        return true;

    }else{
        Toast.makeText(this, "No records available yet!", Toast.LENGTH_LONG).show();
    }

    return super.onOptionsItemSelected(item);
}

@Override
protected void onSaveInstanceState(Bundle outState) {
    SharedPreferences sharedPrefs = getSharedPreferences("Data", Context.MODE_PRIVATE);
    SharedPreferences.Editor editor = sharedPrefs.edit();
    editor.putInt("daily", counter);
    editor.putInt("weekly", counter_weekly);
    editor.commit();
    super.onSaveInstanceState(outState);
    outState.putInt("daily_counter", counter);
    outState.putInt("weekly_counter", counter_weekly);
    ResetVariablesTimers();

}

@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
    counter = savedInstanceState.getInt("daily_counter");
    counter_weekly = savedInstanceState.getInt("weekly_counter");
    TextView daily = (TextView) findViewById(R.id.textView);
    daily.setText(getResources().getString(R.string.beerCount) + counter);
    TextView weekly = (TextView) findViewById(R.id.textView2);
    weekly.setText(getResources().getString(R.string.beerWeek) + counter);
}

@Override
protected void onDestroy() {
    SharedPreferences sharedPrefs = getSharedPreferences("Data", Context.MODE_PRIVATE);
    SharedPreferences.Editor editor = sharedPrefs.edit();
    editor.putInt("daily", counter);
    editor.putInt("weekly", counter_weekly);
    editor.commit();
    super.onDestroy();
    ResetVariablesTimers();
}

@Override
protected void onStop() {
    SharedPreferences sharedPrefs = getSharedPreferences("Data", Context.MODE_PRIVATE);
    SharedPreferences.Editor editor = sharedPrefs.edit();
    editor.putInt("daily", counter);
    editor.putInt("weekly", counter_weekly);
    editor.commit();
    ResetVariablesTimers();

    super.onStop();
}
}

TextView daily_record = (TextView) findViewById(R.id.daily_textview);
TextView weekly_record = (TextView) findViewById(R.id.weekly_textview);

TextView daily_record = (TextView) findViewById(R.id.daily_textview);
TextView weekly_record = (TextView) findViewById(R.id.weekly_textview);