Question

我想在启动应用程序时显示自定义对话框，并且没有任何事件要触发，例如按钮单击。我将自定义对话框放在onCreate()中，但应用程序在NullPointerException处为btnDecline.setOnClickListener处理了。

MainActivity.java

public class MainActivity extends Activity {

    private Button btnRegister, btnDecline, btnAccept;
    private EditText etRegisterName, etRegisterEmail;
    private Dialog terms;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.register);
        btnRegister = (Button)findViewById(R.id.btnRegister);
        etRegisterName = (EditText)findViewById(R.id.etRegisterName);
        etRegisterEmail = (EditText)findViewById(R.id.etRegisterEmail);

        btnRegister.setOnClickListener(new OnClickListener(){
            public void onClick(View v) {
                String name = etRegisterName.getText().toString();
                String email = etRegisterEmail.getText().toString();
            }
        });

        showTermsConditions();
    }

    private void showTermsConditions(){
        terms = new Dialog(MainActivity.this);
        terms.setContentView(R.layout.terms_conditions_dialog);
        btnDecline = (Button) findViewById(R.id.btnDecline);
        btnAccept = (Button) findViewById(R.id.btnAccept);
        terms.setTitle("Terms and Conditions");
        terms.show();

        btnDecline.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                finish();
                moveTaskToBack(true);
            }
        });

        btnAccept.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                terms.dismiss();
            }
        });
    }

}

Answer 1

更改为

terms.setContentView(R.layout.terms_conditions_dialog);
btnDecline = (Button) terms.findViewById(R.id.btnDecline);
btnAccept = (Button) terms.findViewById(R.id.btnAccept);

按钮属于Dialog。您需要在该视图层次结构中查找视图。

findViewById在当前视图层次结构中查找视图。按钮btnDecline和btnAccept不属于register.xml。它们属于terms_conditions_dialog.xml，它是Dialog的布局。

Answer 2

你正在错误的地方看按钮ID

private void showTermsConditions(){
        terms = new Dialog(MainActivity.this);
        terms.setContentView(R.layout.terms_conditions_dialog);
        btnDecline = (Button) terms.findViewById(R.id.btnDecline);
        btnAccept = (Button) terms.findViewById(R.id.btnAccept);
        terms.setTitle("Terms and Conditions");
        terms.show();

        btnDecline.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                finish();
                moveTaskToBack(true);
            }
        });

        btnAccept.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                terms.dismiss();
            }
        });
    }

如何在不点击的情况下立即显示对话框？

2 个答案: