java - java 中的 Android Activity 与 XML 崩溃

Question

我是 Android 开发的新手。我试图显示一个完全用 Java 编写、没有 XML 的简单 Activity ，但它崩溃了。我究竟做错了什么？这是代码:

public class TestActivity extends Activity
{
    @Override
    public void onCreate(Bundle savedinstancestate)
    {
        super.onCreate(savedinstancestate);
        RelativeLayout thislayout = new RelativeLayout(this);
        RelativeLayout.LayoutParams TextViewParams = new RelativeLayout.LayoutParams(
            RelativeLayout.LayoutParams.WRAP_CONTENT,
            RelativeLayout.LayoutParams.WRAP_CONTENT);
        TextViewParams.addRule(RelativeLayout.CENTER_HORIZONTAL);
        TextViewParams.addRule(RelativeLayout.CENTER_VERTICAL);
        TextView outputtext = new TextView(this);
        outputtext.setText("Poop!");
        thislayout.addView(outputtext, TextViewParams);
        setContentView(thislayout);
    }
}

Answer 1

好吧，您正在初始化 LayoutParams，但没有将其设置为 TextView。而且您还必须为父布局定义 LayoutParams ，即 RelativeLayout 。

我测试了您的代码并做了一些更改。 尝试这样做

@Override
public void onCreate(Bundle savedinstancestate) {
    super.onCreate(savedinstancestate);

    // setting RelativeLayout Params
    RelativeLayout thislayout = new RelativeLayout(this);
    LayoutParams params = new LayoutParams(LayoutParams.MATCH_PARENT,
            LayoutParams.MATCH_PARENT);
    thislayout.setLayoutParams(params);

    // setting TextView Params
    TextView outputtext = new TextView(this);
    RelativeLayout.LayoutParams TextViewParams = new RelativeLayout.LayoutParams(
            RelativeLayout.LayoutParams.WRAP_CONTENT,
            RelativeLayout.LayoutParams.WRAP_CONTENT);
    TextViewParams.addRule(RelativeLayout.CENTER_HORIZONTAL);
    TextViewParams.addRule(RelativeLayout.CENTER_VERTICAL);
    outputtext.setLayoutParams(TextViewParams);
    outputtext.setText("Poop!");

    thislayout.addView(outputtext);
    setContentView(thislayout);
}

希望对你有帮助。