Question

我对Android开发人员很陌生，而且我目前正在探索视图可见性，问题在于，当我尝试切换组件的可见性时，我的Android应用程序崩溃了。下面的代码段。

TextView txt;
Button btn;

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

    txt = (TextView) findViewById(R.id.textView1);
    txt.setVisibility(View.VISIBLE);

}
public void toggleVisibility(View view){
    RelativeLayout layout = new RelativeLayout(this);
    String a = getString(txt.getVisibility());
    if(a.equals("GONE")){
        txt.setVisibility(View.VISIBLE);
        layout.addView(txt);
    }
    else{
        txt.setVisibility(View.GONE);
        layout.removeView(txt);
    }

    this.setContentView(layout);
}

使用RelativeLayout的XML文件

 <TextView
    android:id="@+id/textView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:layout_centerVertical="true"
    android:text="@string/hello_world" />

<Button
    android:id="@+id/button1"
    style="?android:attr/buttonStyleSmall"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_above="@+id/textView1"
    android:layout_centerHorizontal="true"
    android:text="Button"
    android:onClick="toggleVisibility" />

<Button
    android:id="@+id/button2"
    style="?android:attr/buttonStyleSmall"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/textView1"
    android:layout_centerHorizontal="true"
    android:text="Button" />

Answer 1

我已在内联添加了答案来解释程序。看看它是否符合您的需求。

如果您还有其他需要解释的地方，请告诉我

  TextView txt;
    Button btn;

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

        // 1 - Here you associated the layout with your new textview. Means that you now hold a reference 
        // to your "txt" textview and that you have set it to be VISIBLE
        txt = (TextView) findViewById(R.id.textView1);
        txt.setVisibility(View.VISIBLE);

    }

    // 2 - you pass the argument view, but you dont really use it, so you can remove the paremeter 
    public void toggleVisibility(View view){

        // 3 - You dont need the new RelativeLayout. Since you already got the reference to the textview
        // and since the TextView is already part of your layout, you can just call methods on it without having to remove and add it again
        // RelativeLayout layout = new RelativeLayout(this);

        // 4 - Dont get visibility from a String like you did
        // String a = getString(txt.getVisibility());
        // So, instead of doing :
        /*
        if(a.equals("GONE")){
            txt.setVisibility(View.VISIBLE);
            layout.addView(txt);
        }
        else{
            txt.setVisibility(View.GONE);
            layout.removeView(txt);
        }
        */
        // You can just get the Visibility of a View using getVisibility() by doing the following : 

        if(txt.getVisiblity == View.VISIBLE) {
            txt.setVisibility(View.GONE);
        } else {
            txt.setVisibility(View.VISIBLE);
        }

        // 5 - The setContentView method is generally meant to attach the Activity's view to the Activity, so you dont need/cant use it here
        // this.setContentView(layout);
    }

切换可见性出错了

1 个答案: