Question

我在childActivity intent中得到了null引用异常。我是android开发的新手。请帮我解决这个问题。我正在做什么来将数据从ParentActivity发送到ChildActivity。

ParentActivity：我在ParentActivity中有3个EditText字段。我想在ChildActivity中显示这3个字段。有一个按钮控件，所以当我点击它时，它必须从ParentActivity切换到ChildActivity。

public class ParentActivity extends Activity {

    private EditText EmpId;
    private EditText EmpName;
    private EditText Gender;
    private Button btnShowInfo;

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

    private void InitializeControls() {
        EmpId = (EditText) findViewById(R.id.editText1);
        EmpName = (EditText) findViewById(R.id.editText2);
        Gender = (EditText) findViewById(R.id.editText3);
        btnShowInfo = (Button) findViewById(R.id.button1);
        final Context context = this;
        btnShowInfo.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {

                Intent ParentIntent = new Intent(context, ChildActivity.class);

                ParentIntent.putExtra("Eid", EmpId.getText().toString());
                ParentIntent.putExtra("EName", EmpName.getText().toString());
                ParentIntent.putExtra("EGender", Gender.getText().toString());
                startActivity(ParentIntent);
            }
        });

    }
}

ChildActivity ::它必须显示我在ParentActivity中输入的值。

public class ChildActivity extends Activity {

    private TextView txtView1;
    private TextView txtView2;
    private TextView txtView3;

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

    private void InitializeControls() {
        txtView1 = (TextView) findViewById(R.id.editText1);
        txtView2 = (TextView) findViewById(R.id.editText2);
        txtView3 = (TextView) findViewById(R.id.editText3);
        GetDataFromIntent();
    }

    private void GetDataFromIntent() {
        Bundle extras = getIntent().getExtras();

        if (extras == null) {
            txtView1.setText("No data is received.");
        } else {

            txtView1.setText(extras.getString("Eid"));
            txtView2.setText(extras.getString("EName"));
            txtView3.setText(extras.getString("EGender"));
        }
    }

}

异常::这是我在控制台窗口中获得的内容。

01-05 15:04:46.210: E/AndroidRuntime(1658): Caused by: java.lang.NullPointerException
01-05 15:04:46.210: E/AndroidRuntime(1658):     at com.example.androidexample1.ChildActivity.GetDataFromIntent(ChildActivity.java:36)
01-05 15:04:46.210: E/AndroidRuntime(1658):     at com.example.androidexample1.ChildActivity.InitializeControls(ChildActivity.java:26)
01-05 15:04:46.210: E/AndroidRuntime(1658):     at com.example.androidexample1.ChildActivity.onCreate(ChildActivity.java:19)

我是android世界的新手。请帮忙。

Answer 1

因此导致问题的代码行是：

txtView1.setText(extras.getString("Eid"));

空指针异常本质上意味着您正在尝试在null的内容上调用函数。在这种情况下，它可以是txtView1或extras。当您检查extra是否为null时，它实际上必须是null的txtView1。每Android documents，findViewById返回：

返回

The view that has the given id in the hierarchy or null

因此，如果拼写错误的文本标签，可能会导致此问题。检查的一个好方法是在错误发生之前添加此权限。

Log.v("Child","txtView1="+txtView1);

从一个intent切换到另一个intent时获取null引用异常

1 个答案: