当我从另一个类调用该方法时，我的应用程序崩溃。

Question

我有个问题，如果有人帮忙，我会很高兴的！

这是崩溃日志：

FATAL EXCEPTION: main
Process: com.elvigo.swedencup.vigor, PID: 29477
java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference
   at android.content.ContextWrapper.getResources(ContextWrapper.java:90)
   at android.view.ContextThemeWrapper.getResourcesInternal(ContextThemeWrapper.java:127)
   at android.view.ContextThemeWrapper.getResources(ContextThemeWrapper.java:121)
   at android.support.v7.app.AppCompatActivity.getResources(AppCompatActivity.java:549)
   at android.view.View.<init>(View.java:4551)
   at android.view.View.<init>(View.java:4694)
   at android.view.ViewGroup.<init>(ViewGroup.java:597)
   at android.widget.LinearLayout.<init>(LinearLayout.java:234)
   at android.widget.LinearLayout.<init>(LinearLayout.java:230)
   at android.widget.LinearLayout.<init>(LinearLayout.java:226)
   at android.widget.LinearLayout.<init>(LinearLayout.java:222)
   at android.widget.TableRow.<init>(TableRow.java:60)
   at com.elvigo.swedencup.vigor.TeamScoreTableUI.addRows(TeamScoreTableUI.java:78)
   at com.elvigo.swedencup.vigor.TeamScoreTableUI.CalladdRows(TeamScoreTableUI.java:65)
   at com.elvigo.swedencup.vigor.Classes.MatchTableDataFeatching.onPostExecute(MatchTableDataFeatching.java:139)
   at com.elvigo.swedencup.vigor.Classes.MatchTableDataFeatching.onPostExecute(MatchTableDataFeatching.java:26)
   at android.os.AsyncTask.finish(AsyncTask.java:695)
   at android.os.AsyncTask.-wrap1(Unknown Source:0)
   at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:712)
   at android.os.Handler.dispatchMessage(Handler.java:105)
   at android.os.Looper.loop(Looper.java:164)
   at android.app.ActivityThread.main(ActivityThread.java:6809)
   at java.lang.reflect.Method.invoke(Native Method)
   at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)

以及包括被调用方法在内的活动：

public class TeamScoreTableUI extends AppCompatActivity {

public static TextView TextBox;
FloatingActionButton PrevScreenBtn;
public static TableLayout ll;


public static TextView textView;
public static TableRow row;


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


    MatchTableDataFeatching process = new MatchTableDataFeatching();
    process.execute();


    TextBox = (TextView) findViewById(R.id.TextBox);
    PrevScreenBtn = (FloatingActionButton) findViewById(R.id.BackButton);

    PrevScreenBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            finish();

        }
    });

    Context context = getApplicationContext();
    Toast toast = Toast.makeText(context, "FairPlayCup", Toast.LENGTH_SHORT);
    toast.show();

    ll = (TableLayout) findViewById(R.id.TableLayout);


}

public void CalladdRows(){

    addRows();

}


public void addRows() {



    //for (int i = 0; i < 2; i++) {

        Log.d("dataFeatchingDone", "done");

        row = new TableRow(this);
        TableRow.LayoutParams lp = new TableRow.LayoutParams(TableRow.LayoutParams.WRAP_CONTENT);
        row.setLayoutParams(lp);
        TextView textView = new TextView(this);
        textView.setText("10");
        row.addView(textView);
        ll.addView(row, 1);
    //}

}
}

我还在调试模式下测试了这个应用程序，我发现它在: row =(这个)上崩溃了；

我正在调用"CalladdRows()“方法。

我用以下方式调用该方法：

@Override
protected void onPostExecute(Void aVoid) {
    super.onPostExecute(aVoid);

    Log.d("app", "onPostExecute");

    TeamScoreTableUI.TextBox.setText(this.dataParsed);

    TeamScoreTableUI TeamScoreTableUIAddRows = new TeamScoreTableUI();
    TeamScoreTableUIAddRows.CalladdRows();

}

该方法在TeamScoreTableUI中，称为CalladdRows。

如果有人能花点时间帮忙，我会很高兴的！

Answer 1

尝试使用以下更改：

1. Pass context to your Task

MatchTableDataFeatching process = new MatchTableDataFeatching(this);

2. Get context in your Task

Context context;
public MatchTableDataFeatching(Context c) {
    context = c;
}
.......
3. Then in your onPost

@Override
protected void onPostExecute(Void aVoid) {
    super.onPostExecute(aVoid);
    ((TeamScoreTableUI)context).TextBox.setText(this.dataParsed);
    ((TeamScoreTableUI)context).CalladdRows();

}

Answer 2

在你的代码中

TeamScoreTableUI.TextBox.setText(this.dataParsed);

TeamScoreTableUI TeamScoreTableUIAddRows = new TeamScoreTableUI();
TeamScoreTableUIAddRows.CalladdRows();

您错误地创建了一个新活动，并在这个新创建的活动上调用"CalladdRows()“(而不是使用与设置"TextBox”相同的活动。

尝试将您的代码更改为

TeamScoreTableUI.TextBox.setText(this.dataParsed);       
TeamScoreTableUI.CalladdRows()

作为旁注

字段和方法名称中的大写大小写使代码难以阅读。我在找出asyncTask中的TeamScoreTableUI/TextBox是字段还是静态类时遇到了问题。

在JAVA中，通常使用小写字母(camelCase)作为字段、变量和方法名称；大写字母(PascalCase)用于类。