java - 我的应用程序运行良好，但 TextView 不会显示

Question

我正在制作我的应用程序的首页。不幸的是，只有 TextView 不会显示。按钮和后台运行得很好。我什至使用 addView() 函数将其添加到相对布局中。有人可以帮忙吗？

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    //layout
    RelativeLayout mainLayout = new RelativeLayout(this);
    mainLayout.setBackgroundColor(Color.BLUE);

    //button
    Button mainButton = new Button (this);
    mainButton.setText("Next");
    mainButton.setBackgroundColor(Color.RED);

    //textview
    TextView mainTextView = new TextView(this);
    mainTextView.setText("Juliet Daniel Lab Molecular Biology Cancer Research Center");
    mainTextView.setTextSize(30);
    mainTextView.setBackgroundColor(Color.GREEN);

    //sizing the button
    RelativeLayout.LayoutParams btnDetails = new RelativeLayout.LayoutParams(
            RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT
    );
    //sizing the textview
    RelativeLayout.LayoutParams textViewDetails = new RelativeLayout.LayoutParams(
            RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT
    );

    //give id's to position relatively...note it is preferable to do this in the res folder to avoid errors
    mainButton.setId(1);
    mainTextView.setId(2);

    //give rules to position widgets relatively
    textViewDetails.addRule(RelativeLayout.ABOVE, mainButton.getId());
    textViewDetails.addRule(RelativeLayout.CENTER_HORIZONTAL);
    textViewDetails.setMargins(0,0,0,50);


    //adding the button as a part of the RelativeLayout (ADDING THE BUTTON WIDGET TO LAYOUT)
    mainLayout.addView(mainButton, btnDetails);
    //adding the textview as a part of the relative Layout
    mainLayout.addView(mainTextView, textViewDetails);

    //setting the view as out layour
    setContentView(mainLayout);

}
}

Answer 1

这是因为您在按钮上方设置了 textview，其中 button 是根布局的第一个顶部，这就是为什么它没有显示尝试在下面设置 textview按钮就可以了

textViewDetails.addRule(RelativeLayout.BELOW, mainButton.getId());