用戶觸摸屏時按鈕無法從左上角移動到右下角

Question

我希望按鈕更改其大小並在用戶觸摸屏幕時從左上方移動到右下方。但是，當我觸摸屏幕時，我的應用會停止運行。如果我刪除了更改按鈕位置的部分代碼，一切正常，按鈕更改其位置尺寸。

這是MainActivity.java

package com.example.user.a34;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.RelativeLayout;


public class MainActivity extends AppCompatActivity {

    ViewGroup main_layout;

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

        main_layout = (ViewGroup)findViewById(R.id.main_layout);
        main_layout.setOnTouchListener(new RelativeLayout.OnTouchListener(){
            public boolean onTouch(View v,MotionEvent event){
                moveButton();
                return true;
            }
        });
    }

    public void moveButton(){
        View button1 = (View)findViewById(R.id.button1);

        //Change position---------------------
        RelativeLayout.LayoutParams positionRules = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT);
        positionRules.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM, RelativeLayout.TRUE);
        positionRules.addRule(RelativeLayout.ALIGN_PARENT_RIGHT, RelativeLayout.TRUE);
        button1.setLayoutParams(positionRules);

        //Change size-------------------------
        ViewGroup.LayoutParams sizeRules = button1.getLayoutParams();
        sizeRules.width = 350;
        sizeRules.height = 200;
        button1.setLayoutParams(sizeRules);

    }
}

這是activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.user.a34.MainActivity">

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button"
        app:layout_constraintTop_toTopOf="parent"
        android:layout_marginTop="38dp"
        android:layout_marginLeft="66dp"
        app:layout_constraintLeft_toLeftOf="parent" />
</android.support.constraint.ConstraintLayout>

Answer 1

崩潰的直接原因可能是試圖將RelativeLayout.LayoutParams分配給ConstraintLayout的視圖，因此應該具有ConstraintLayout.LayoutParams類型的布局參數。

您要么需要在xml中使用RelativeLayout ，要么分配類型為ConstraintLayout.LayoutParams按鈕布局參數。

我建議在您的xml中使用RelativeLayout ，如下所示：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.user.a34.MainActivity">

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button"
        android:layout_marginTop="38dp"
        android:layout_marginBottom="38dp"
        android:layout_marginLeft="66dp"
        android:layout_marginRight="66dp"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true" />

</RelativeLayout>

並如下更改您的moveButton方法：

public void moveButton() {
        View button1 = findViewById(R.id.button1);

        RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams)button1.getLayoutParams();
        layoutParams.removeRule(RelativeLayout.ALIGN_PARENT_TOP);
        layoutParams.removeRule(RelativeLayout.ALIGN_PARENT_LEFT);
        layoutParams.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM, RelativeLayout.TRUE);
        layoutParams.addRule(RelativeLayout.ALIGN_PARENT_RIGHT, RelativeLayout.TRUE);
        layoutParams.width = 350;
        layoutParams.height = 200;
        button1.setLayoutParams(layoutParams);
}