为 TextView 赋值时的空值

Question

我已经研究这个问题好几个小时了。我很确定我正确地将值 saveLeagueId 分配给了 TextView。我想要做的是将一个值从 MainActivity 传递到 BowlerActivity。这是我的代码，它使用意图传递值；@Override            public void onClick(View view, final int position) {                int leagueId = leaguesList.get(position).getId();                String savedLeagueId = String.valueOf( leagueId );                Intent myIntent = new Intent(MainActivity.this, BowlerActivity.class);                Log.d("Passing League Id ", "Passed Value is " + leagueId);                myIntent.putExtra("leagueId", savedLeagueId);                startActivity(myIntent);                overridePendingTransition(0, 0);            }我可以看到它实际上是将值传递给 BowlerActivity2019-07-09 20:47:06.694 8596-8596/ca.vogl.r.tenpinbowlingcompanion D/Passing League Id: Passed Value is 22019-07-09 20:47:06.777 8596-8596/ca.vogl.r.tenpinbowlingcompanion D/GETALLBOWLERS-SQL: SQL used = >>>>SELECT  * FROM bowlers WHERE league_id = 'null' ORDER BY timestamp DESC<<<<2019-07-09 20:47:06.785 8596-8596/ca.vogl.r.tenpinbowlingcompanion D/GETALLBOWLERS-CNT: Number of rows retrieved = 02019-07-09 20:47:06.786 8596-8596/ca.vogl.r.tenpinbowlingcompanion D/GETALLBOWLERS-CNT: Number of elements in bowlerslist = 02019-07-09 20:47:06.786 8596-8596/ca.vogl.r.tenpinbowlingcompanion D/SAVEDLEAGUEID --->: 2但是，当我尝试将值传递给名为 leagueId 的 TextView 时，它为空。

Answer 1

正如我注意到的，您的 Dialog 窗口中有leagueIdtextView。因此，请确保您的布局文件tvLeagueId中有一个带有 id的 textView activity_bowlers_dialog。

然后在你的openDialog函数中使用view.findViewById引用 textview

public void openDialog(final boolean shouldUpdate, final Bowler bowler, final int position) {

        LayoutInflater layoutInflaterAndroid = LayoutInflater.from(getApplicationContext());

        View view = View.inflate(this, R.layout.activity_bowlers_dialog, null);

        leagueId = view.findViewById(R.id.tvLeagueId); // <-- Add this line

        AlertDialog.Builder alertDialogBuilderUserInput = new AlertDialog.Builder(BowlerActivity.this);

        alertDialogBuilderUserInput.setView(view);

        leagueId.setText(savedLeagueId);

        final EditText inputBowler = view.findViewById(R.id.etBowlerName);

        // rest of the code

Answer 2

它与如何从返回 null 的 findViewById 中获取 TextView 的意图没有任何问题。

java.lang.NullPointerException：尝试在* 空对象引用上调用虚拟方法“void android.widget.TextView.setText(java.lang.CharSequence)” *