我是Android编程的新手。在这里，我有一个带有背部，快速菜单和确定按钮的页脚。 通过按下菜单按钮，我想要另一个线性布局向上滑动。再次按下它会滑下来。
BaseActivity：
package com.app.getconnected.activities;
import com.app.getconnected.R;
import com.app.getconnected.animations.CollapseAnimation;
import com.app.getconnected.animations.ExpandAnimation;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.util.DisplayMetrics;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.TextView;
abstract class BaseActivity extends Activity {
protected TextView txtHeading;
protected Button buttonBack;
private Button buttonMenu;
protected Button buttonOk;
protected Button buttonHome;
private LinearLayout MenuList;
private int screenHeight;
private boolean isExpanded;
protected static final String activityPackage = "com.app.getconnected.activities";
protected static Boolean loggedIn=false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.footer);
}
protected void initLayout(int resId, boolean homeButton,
boolean backButton, boolean menuButton, boolean okButton) {
if (txtHeading == null)
txtHeading = (TextView) findViewById(R.id.header_text);
if (txtHeading != null)
txtHeading.setText(resId);
buttonHome = (Button) findViewById(R.id.header_button_home);
buttonBack = (Button) findViewById(R.id.footer_button_back);
buttonMenu = (Button) findViewById(R.id.footer_button_menu);
buttonOk = (Button) findViewById(R.id.footer_button_ok);
buttonBack.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
goBack();
}
});
buttonMenu.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
handleMenu();
}
});
buttonHome.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(BaseActivity.this,
MainActivity.class);
startActivityForResult(intent, 1);
finish();
}
});
this.buttonHome.setVisibility(homeButton ? View.VISIBLE
: View.INVISIBLE);
this.buttonBack.setVisibility(backButton ? View.VISIBLE
: View.INVISIBLE);
this.buttonMenu.setVisibility(menuButton ? View.VISIBLE
: View.INVISIBLE);
this.buttonOk.setVisibility(okButton ? View.VISIBLE : View.INVISIBLE);
}
protected void goBack() {
super.onBackPressed();
}
private void handleMenu() {
DisplayMetrics metrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(metrics);
screenHeight = metrics.heightPixels;
buttonMenu.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
System.out.println("Quick Menu clicked");
if (isExpanded) {
isExpanded = false;
MenuList.startAnimation(new CollapseAnimation(MenuList, 0, (int)(screenHeight*0.7), 20));
}else {
isExpanded = true;
MenuList.startAnimation(new ExpandAnimation(MenuList, 0,(int)(screenHeight*0.7), 20));
}
}
});
}
protected void disableBackButton() {
}
/**
*
* @param view
*/
public void startIntentByButton(View view) {
Button button = (Button) view;
if(!button.getTag().equals("")) {
try {
Intent intent = new Intent(getApplicationContext(), Class.forName(BaseActivity.activityPackage + "." + button.getTag().toString()));
startActivityForResult(intent, 1);
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
}
}
以下是两个动画类。
崩溃：
package com.app.getconnected.animations;
import android.view.View;
import android.view.ViewGroup.LayoutParams;
import android.view.animation.AccelerateInterpolator;
import android.view.animation.Animation;
public class CollapseAnimation extends Animation implements Animation.AnimationListener {
private View view;
private static int ANIMATION_DURATION;
private int LastWidth;
private int FromWidth;
private int ToWidth;
private static int STEP_SIZE=30;
public CollapseAnimation(View v, int FromWidth, int ToWidth, int Duration) {
this.view = v;
LayoutParams lyp = view.getLayoutParams();
ANIMATION_DURATION = 1;
this.FromWidth = lyp.height;
this.ToWidth = lyp.height;
setDuration(ANIMATION_DURATION);
setRepeatCount(20);
setFillAfter(false);
setInterpolator(new AccelerateInterpolator());
setAnimationListener(this);
}
@Override
public void onAnimationEnd(Animation animation) {
// TODO Auto-generated method stub
}
@Override
public void onAnimationRepeat(Animation animation) {
// TODO Auto-generated method stub
LayoutParams lyp = view.getLayoutParams();
lyp.height = lyp.height - ToWidth/20;
view.setLayoutParams(lyp);
}
@Override
public void onAnimationStart(Animation animation) {
// TODO Auto-generated method stub
LayoutParams lyp = view.getLayoutParams();
LastWidth = lyp.height;
}
}
扩展：
package com.app.getconnected.animations;
import android.view.View;
import android.view.ViewGroup.LayoutParams;
import android.view.animation.AccelerateInterpolator;
import android.view.animation.Animation;
import android.widget.Toast;
public class ExpandAnimation extends Animation implements Animation.AnimationListener {
private View view;
private static int ANIMATION_DURATION;
private int LastWidth;
private int FromWidth;
private int ToWidth;
private static int STEP_SIZE=30;
public ExpandAnimation(View v, int FromWidth, int ToWidth, int Duration) {
this.view = v;
ANIMATION_DURATION = 1;
this.FromWidth = FromWidth;
this.ToWidth = ToWidth;
setDuration(ANIMATION_DURATION);
setRepeatCount(20);
setFillAfter(false);
setInterpolator(new AccelerateInterpolator());
setAnimationListener(this);
}
@Override
public void onAnimationEnd(Animation animation) {
// TODO Auto-generated method stub
}
@Override
public void onAnimationRepeat(Animation animation) {
// TODO Auto-generated method stub
LayoutParams lyp = view.getLayoutParams();
lyp.height = LastWidth += ToWidth/20;
view.setLayoutParams(lyp);
}
@Override
public void onAnimationStart(Animation animation) {
// TODO Auto-generated method stub
LayoutParams lyp = view.getLayoutParams();
lyp.height = 0;
view.setLayoutParams(lyp);
LastWidth = 0;
}
}
logcat的：
10-24 09:08:52.210: D/dalvikvm(1095): GC_FOR_ALLOC freed 159K, 9% free 2860K/3120K, paused 41ms, total 59ms
10-24 09:08:52.350: D/gralloc_goldfish(1095): Emulator without GPU emulation detected.
10-24 09:08:56.489: D/dalvikvm(1095): GC_FOR_ALLOC freed 50K, 5% free 3321K/3472K, paused 51ms, total 68ms
10-24 09:09:14.550: I/System.out(1095): Quick Menu clicked
10-24 09:09:14.580: D/AndroidRuntime(1095): Shutting down VM
10-24 09:09:14.580: W/dalvikvm(1095): threadid=1: thread exiting with uncaught exception (group=0x414c4700)
10-24 09:09:14.680: E/AndroidRuntime(1095): FATAL EXCEPTION: main
10-24 09:09:14.680: E/AndroidRuntime(1095): java.lang.NullPointerException
10-24 09:09:14.680: E/AndroidRuntime(1095): at com.app.getconnected.activities.BaseActivity$4.onClick(BaseActivity.java:109)
10-24 09:09:14.680: E/AndroidRuntime(1095): at android.view.View.performClick(View.java:4240)
10-24 09:09:14.680: E/AndroidRuntime(1095): at android.view.View$PerformClick.run(View.java:17721)
10-24 09:09:14.680: E/AndroidRuntime(1095): at android.os.Handler.handleCallback(Handler.java:730)
10-24 09:09:14.680: E/AndroidRuntime(1095): at android.os.Handler.dispatchMessage(Handler.java:92)
10-24 09:09:14.680: E/AndroidRuntime(1095): at android.os.Looper.loop(Looper.java:137)
10-24 09:09:14.680: E/AndroidRuntime(1095): at android.app.ActivityThread.main(ActivityThread.java:5103)
10-24 09:09:14.680: E/AndroidRuntime(1095): at java.lang.reflect.Method.invokeNative(Native Method)
10-24 09:09:14.680: E/AndroidRuntime(1095): at java.lang.reflect.Method.invoke(Method.java:525)
10-24 09:09:14.680: E/AndroidRuntime(1095): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
10-24 09:09:14.680: E/AndroidRuntime(1095): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
10-24 09:09:14.680: E/AndroidRuntime(1095): at dalvik.system.NativeStart.main(Native Method)
10-24 09:11:49.983: I/Process(1095): Sending signal. PID: 1095 SIG: 9
10-24 09:11:52.441: D/gralloc_goldfish(1125): Emulator without GPU emulation detected.
非常欢迎任何帮助或建议，
丹尼尔
答案 0 :(得分：2)
就像@Mike在评论中所说，你需要启动MenuList对象。
MenuList = (LinearLayout)this.findViewById(R.id.menu_list_layout);
忽略this，尤其是如果您将此行放在onClick中。将行放在启动按钮的位置，然后删除this