我真的是 Android 编程的新手，我的代码有任何错误，如果这段代码有问题，有人可以帮忙吗？日志猫向我显示了这些错误：
08-07 11:59:46.773: E/AndroidRuntime(26185): java.lang.RuntimeException: Unable to start activity
ComponentInfo{uiv.makedirect.activity/uiv.makedirect.activity.ManagerActivity}: java.lang.NullPointerException
08-07 11:59:46.773: E/AndroidRuntime(26185): at uiv.makedirect.utilities.RadioStateDrawable.<init>(RadioStateDrawable.java:78)
08-07 11:59:46.773: E/AndroidRuntime(26185): at uiv.makedirect.utilities.TabBarButton.setState(TabBarButton.java:66)
我的代码：我用于创建 Tabactivity 的活动：
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
/*
* set this activity as the tab bar delegate so that onTabChanged is called when users tap on the bar
*/
setDelegate(new SliderBarActivityDelegateImpl());
Intent home = new Intent(this, HomeActivity.class);
Intent feed = new Intent(this, FeedActivity.class);
Intent cart = new Intent(this, CartActivity.class);
Intent invite = new Intent(this, InviteActivity.class);
Intent account = new Intent(this, AccountActivity.class);
/*
* This adds a title and an image to the tab bar button Image should be a PNG file with transparent background. Shades are opaque areas in on and off state are specific as parameters
*/
this.addTab("Home", R.drawable.star, RadioStateDrawable.SHADE_GRAY, RadioStateDrawable.SHADE_BLUE, home);
this.addTab("Feed", R.drawable.icon_feed, RadioStateDrawable.SHADE_GRAY, RadioStateDrawable.SHADE_BLUE, feed);
this.addTab("Cart", R.drawable.ico_cart, RadioStateDrawable.SHADE_GRAY, RadioStateDrawable.SHADE_BLUE, cart);
this.addTab("Invite", R.drawable.ico_invite, RadioStateDrawable.SHADE_GRAY, RadioStateDrawable.SHADE_BLUE, invite);
this.addTab("Account", R.drawable.star, RadioStateDrawable.SHADE_GRAY, RadioStateDrawable.SHADE_BLUE, account);
/*
* commit is required to redraw the bar after add tabs are added if you know of a better way, drop me your suggestion please.
*/
commit();
}
ScrollableTabActivity：
public class ScrollableTabActivity extends ActivityGroup implements RadioGroup.OnCheckedChangeListener{
private LocalActivityManager activityManager;
private LinearLayout contentViewLayout;
private LinearLayout.LayoutParams contentViewLayoutParams;
private HorizontalScrollView bottomBar;
private RadioGroup.LayoutParams buttonLayoutParams;
private RadioGroup bottomRadioGroup;
private Context context;
private List intentList;
private List titleList;
private List states;
private SliderBarActivityDelegate delegate;
private int defaultOffShade;
private int defaultOnShade;
private IntentFilter changeTabIntentFilter;
private ChangeTabBroadcastReceiver changeTabBroadcastReceiver;
public static String CURRENT_TAB_INDEX;
public static String ACTION_CHANGE_TAB = "com.mobyfactory.changeTab";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
context = this;
activityManager = getLocalActivityManager();
setContentView(R.layout.customslidingtabhost);
contentViewLayout = (LinearLayout)findViewById(R.id.contentViewLayout);
bottomBar = (HorizontalScrollView)findViewById(R.id.bottomBar);
bottomRadioGroup = (RadioGroup)findViewById(R.id.bottomMenu);
contentViewLayoutParams = new LinearLayout.LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT);
defaultOffShade = RadioStateDrawable.SHADE_GRAY;
defaultOnShade = RadioStateDrawable.SHADE_YELLOW;
bottomRadioGroup.setOnCheckedChangeListener(this);
intentList = new ArrayList();
titleList = new ArrayList();
states = new ArrayList();
buttonLayoutParams = new RadioGroup.LayoutParams(320/5, RadioGroup.LayoutParams.WRAP_CONTENT);
}
public void onResume()
{
changeTabIntentFilter = new IntentFilter(ACTION_CHANGE_TAB);
changeTabBroadcastReceiver = new ChangeTabBroadcastReceiver();
registerReceiver(changeTabBroadcastReceiver, changeTabIntentFilter);
super.onResume();
}
public void onPause()
{
unregisterReceiver(changeTabBroadcastReceiver);
super.onPause();
}
public void commit()
{
bottomRadioGroup.removeAllViews();
int optimum_visible_items_in_portrait_mode = 5;
try
{
WindowManager window = getWindowManager();
Display display = window.getDefaultDisplay();
int window_width = display.getWidth();
optimum_visible_items_in_portrait_mode = (int) (window_width/64.0);
}
catch (Exception e)
{
optimum_visible_items_in_portrait_mode = 5;
}
int screen_width = getWindowManager().getDefaultDisplay().getWidth();
int width;
if (intentList.size()<=optimum_visible_items_in_portrait_mode)
{
width = screen_width/intentList.size();
}
else
{
width = screen_width/5;
//width = 320/5;
}
RadioStateDrawable.width = width;
RadioStateDrawable.screen_width = screen_width;
buttonLayoutParams = new RadioGroup.LayoutParams(width, RadioGroup.LayoutParams.WRAP_CONTENT);
for (int i=0; i<intentList.size(); i++)
{
TabBarButton tabButton = new TabBarButton(this);
int[] iconStates = (int[]) states.get(i);
if (iconStates.length==1)
tabButton.setState( titleList.get(i).toString(),iconStates[0]);
else if (iconStates.length==2)
tabButton.setState(titleList.get(i).toString(), iconStates[0], iconStates[1]);
else if (iconStates.length==3)
tabButton.setState(titleList.get(i).toString(), iconStates[0], iconStates[1], iconStates[2]);
tabButton.setId(i);
tabButton.setGravity(Gravity.CENTER);
bottomRadioGroup.addView(tabButton, i, buttonLayoutParams);
}
setCurrentTab(0);
}
protected void addTab(String title, int offIconStateId, int onIconStateId, Intent intent)
{
int[] iconStates = {onIconStateId, offIconStateId};
states.add(iconStates);
intentList.add(intent);
titleList.add(title);
//commit();
}
protected void addTab(String title, int iconStateId, Intent intent)
{
//int[] iconStates = {iconStateId};
int[] iconStates = {iconStateId, defaultOffShade, defaultOnShade};
states.add(iconStates);
intentList.add(intent);
titleList.add(title);
//commit();
}
protected void addTab(String title, int iconStateId, int offShade, int onShade, Intent intent)
{
int[] iconStates = {iconStateId, offShade, onShade};
states.add(iconStates);
intentList.add(intent);
titleList.add(title);
//commit();
}
和 RadioStateDrawable 用于在选项卡中显示图像：
public class RadioStateDrawable extends Drawable {
private Bitmap bitmap;
private Bitmap highlightBitmap;
private Shader shader;
private Shader textShader;
Context context;
public static int width;
public static int screen_width;
private boolean highlight;
private String label;
public static final int SHADE_GRAY = 0;
public static final int SHADE_BLUE = 1;
public static final int SHADE_MAGENTA = 2;
public static final int SHADE_YELLOW = 3;
public static final int SHADE_GREEN = 4;
public static final int SHADE_RED = 5;
public static final int SHADE_ORANGE = 6;
public RadioStateDrawable(Context context, int imageID, String label, boolean highlight, int shade)
{
super();
this.highlight = highlight;
this.context = context;
this.label = label;
InputStream is = context.getResources().openRawResource(imageID);
bitmap = BitmapFactory.decodeStream(is).extractAlpha();
setShade(shade);
highlightBitmap = BitmapFactory.decodeResource(context.getResources(), R.drawable.bottom_bar_highlight);
}
public RadioStateDrawable(Context context, int imageID, String label, boolean highlight, int startGradientColor, int endGradientColor)
{
super();
this.highlight = highlight;
this.context = context;
this.label = label;
InputStream is = context.getResources().openRawResource(imageID);
bitmap = BitmapFactory.decodeStream(is).extractAlpha();
int[] shades = new int[] { startGradientColor, endGradientColor };
shader = new LinearGradient(0, 0, 0, bitmap.getHeight(), shades, null, Shader.TileMode.MIRROR);
}
public void setShade(int shade)
{
int[] shades = new int[2];
switch (shade)
{
case SHADE_GRAY: {
shades = new int[] { Color.LTGRAY, Color.DKGRAY };
break;
}
case SHADE_BLUE: {
shades = new int[] { Color.CYAN, Color.BLUE };
break;
}
case SHADE_RED: {
shades = new int[] { Color.MAGENTA, Color.RED };
break;
}
case SHADE_MAGENTA: {
shades = new int[] { Color.MAGENTA, Color.rgb(292, 52, 100) };
break;
}
case SHADE_YELLOW: {
shades = new int[] { Color.YELLOW, Color.rgb(255, 126, 0) };
break;
}
case SHADE_ORANGE: {
shades = new int[] { Color.rgb(255, 126, 0), Color.rgb(255, 90, 0) };
break;
}
case SHADE_GREEN: {
shades = new int[] { Color.GREEN, Color.rgb(0, 79, 4) };
break;
}
}
shader = new LinearGradient(0, 0, 0, bitmap.getHeight(), shades, null, Shader.TileMode.MIRROR);
if (highlight)
textShader = new LinearGradient(0, 0, 0, 10, new int[] { Color.WHITE, Color.LTGRAY }, null, Shader.TileMode.MIRROR);
else
textShader = new LinearGradient(0, 0, 0, 10, new int[] { Color.LTGRAY, Color.DKGRAY }, null, Shader.TileMode.MIRROR);
}
@Override
public void draw(Canvas canvas) {
int bwidth = bitmap.getWidth();
int bheight = bitmap.getHeight();
/*
* if (width==0) { if (screen_width==0) screen_width = 320; width=screen_width/5; }
*/
int x = (width - bwidth) / 2;
int y = 2;
canvas.drawColor(Color.TRANSPARENT);
Paint p = new Paint();
p.setColor(Color.WHITE);
p.setStyle(Paint.Style.FILL);
p.setTextSize(19);
p.setTypeface(Typeface.DEFAULT_BOLD);
p.setFakeBoldText(true);
p.setTextAlign(Align.CENTER);
p.setShader(textShader);
p.setAntiAlias(true);
canvas.drawText(label, width / 2, y + bheight + 20, p);
p.setShader(shader);
canvas.drawBitmap(bitmap, x, y, p);
}
更改图像选项卡时出现错误