通过在触摸屏上拖动切换屏幕

Question

我曾尝试过通过拖动触摸屏来切换屏幕的代码。。但它给出了一个错误。。。谁能检查一下我在代码中犯了什么错误吗。。出现错误

vf.setInAnimation（AnimationUtils.loadAnimation（this，R.anim.push_left_in）；vf.setInAnimation（AnimationUtils.loadAnimation（this，R.anim.push_left_out）；

.xml文件的代码

<ViewFlipper android:id="@+id/details"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">  
    <LinearLayout
        android:orientation="vertical"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:background="#ffffff">
        <TextView android:id="@+id/tv_country"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:textColor="#000000"
            android:textStyle="bold"
            android:textSize="18px"
            android:text="Country" >
        </TextView>
        <Spinner android:text=""
            android:id="@+id/spinner_country"
            android:layout_width="200px"
            android:layout_height="55px">
        </Spinner>
    </LinearLayout> 
    <LinearLayout
        android:orientation="vertical"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:background="#ffffff">
        <TextView android:id="@+id/tv_income"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:textColor="#000000"
            android:textStyle="bold"
            android:textSize="18px"
            android:text="Income" >
        </TextView>
        <EditText android:text=""
            android:id="@+id/et_income"
            android:layout_width="200px"
            android:layout_height="55px">
        </EditText>
    </LinearLayout> 
</ViewFlipper>

.java文件的代码

package com.examples.switchactivtybydragging;
import android.app.Activity;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.view.animation.*;
import android.widget.ArrayAdapter;
import android.widget.LinearLayout;
import android.widget.Spinner;
import android.widget.ViewFlipper;
public class SwitchActivityByDraggingActivity extends Activity implements OnTouchListener {
    /** Called when the activity is first created. */
    private float downXValue;
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        LinearLayout layMain = (LinearLayout) findViewById(R.id.layout_main);
        layMain.setOnTouchListener((OnTouchListener) this);
        Spinner spinnerCountries = (Spinner) findViewById(R.id.spinner_country);
        @SuppressWarnings({ "unchecked", "rawtypes" })
        ArrayAdapter countryArrayAdapter = new ArrayAdapter(this,
                    android.R.layout.simple_spinner_dropdown_item,
                    new String[] { "Canada", "USA" });
        spinnerCountries.setAdapter(countryArrayAdapter);
    }
    public boolean onTouch(View arg0, MotionEvent arg1) {
        // Get the action that was done on this touch event
        switch (arg1.getAction())
        {
            case MotionEvent.ACTION_DOWN:
            {
                // store the X value when the user's finger was pressed down
                downXValue = arg1.getX();
                break;
            }
            case MotionEvent.ACTION_UP:
            {
                // Get the X value when the user released his/her finger
                float currentX = arg1.getX();            
                // going backwards: pushing stuff to the right
                if (downXValue < currentX)
                {
                    // Get a reference to the ViewFlipper
                     ViewFlipper vf = (ViewFlipper) findViewById(R.id.details);
                     // Set the animation
                      vf.setAnimation(AnimationUtils.loadAnimation(this,R.anim.push_left_out));
                      // Flip!
                      vf.showPrevious();
                }
                // going forwards: pushing stuff to the left
                if (downXValue > currentX)
                {
                    // Get a reference to the ViewFlipper
                    ViewFlipper vf = (ViewFlipper) findViewById(R.id.details);
                     // Set the animation
                     vf.setInAnimation(AnimationUtils.loadAnimation(this,R.anim.push_left_in));
                      // Flip!
                     vf.showNext();
                }
                break;
            }
        }
        // if you return false, these actions will not be recorded
        return true;
    }
}

Answer 1

您的问题是尚未创建动画。为了使代码正常工作，您需要res/anim/push_left_in.xml和res/anim/push_left_out.xml中的动画。正是这些文件的缺失导致了您的错误。

我写了一个关于简单动画的博客系列，可以帮助你了解如何创建这些文件，以及你需要在其中放入什么。