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我正在使用此approach。我做了所有的步驟中顯示的自定義開關在Android 2.3或以上顯示。但是當我運行該應用程序拋出一個錯誤，我在下面顯示。我也展示了我使用的那個類，並提到了發生錯誤的那一行。我在attr和styles中應用了代碼。請提前幫助我。Android：在自定義開關佈局上發生錯誤
類其中放在com.app.widgets包。
public class Switch extends CompoundButton
{
// left and right text
private CharSequence textLeft;
private CharSequence textRight;
public Context c;
// the background
private Drawable drawableBackground;
// the switch
private Drawable drawableSwitch;
// helper for left and right text
private Layout layoutLeft;
private Layout layoutRight;
// min width of the whole switch
private int switchMinWidth;
// actual width and height of the switch
private int width;
private int height;
// the padding left+right inside of the switch
private int innerPadding;
// the space between the text to the left of the switch and the switch
private int switchPadding;
// the colors for the text of the switch
private int textColorChecked;
private int textColorUnChecked;
private OnClickListener onClickListener;
public Switch(Context context) {
this(context, null);
c = context;
}
public Switch(Context context, AttributeSet attrs) {
this(context, attrs, R.attr.switchStyle);
Log.e("log", "in Switch(Context context, AttributeSet attrs)");
c = context;
}
public Switch(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
c = context;
this.getPaint().setAntiAlias(true);
Log.e("log",
"in Switch(Context context, AttributeSet attrs, int defStyle)");
// load the default values
TypedArray a = context.obtainStyledAttributes(attrs,
R.styleable.Switch, defStyle, 0);
this.textLeft = a.getText(R.styleable.Switch_textLeft);
this.textRight = a.getText(R.styleable.Switch_textRight);
this.switchMinWidth = a.getDimensionPixelSize(
R.styleable.Switch_switchMinWidth, 250);
this.textColorUnChecked = a.getColor(R.styleable.Switch_colorUnChecked,
Color.WHITE);
this.textColorChecked = a.getColor(R.styleable.Switch_colorChecked,
Color.WHITE);
this.drawableBackground = a
.getDrawable(R.styleable.Switch_backgroundDrawable);
this.drawableSwitch = a.getDrawable(R.styleable.Switch_switchDrawable);
this.switchPadding = a.getDimensionPixelSize(
R.styleable.Switch_switchPadding, 32);
this.innerPadding = a.getDimensionPixelSize(
R.styleable.Switch_innerPadding, 20);
this.setChecked(a.getBoolean(R.styleable.Switch_isChecked, false));
a.recycle();
// throw an error if the texts have not been set
if (this.textLeft == null || this.textRight == null)
throw new IllegalStateException(
"Either textLeft or textRight is null. Please them via the attributes with the same name in the layout");
}
public void setTextLeft(CharSequence textLeft) {
if (textLeft == null)
throw new IllegalArgumentException(
"The text for the left side must not be null!");
this.textLeft = textLeft;
this.requestLayout();
}
public CharSequence getTextLeft() {
return this.textLeft;
}
public CharSequence getTextRight() {
return this.textRight;
}
public void setTextRight(CharSequence textRight) {
if (textRight == null)
throw new IllegalArgumentException(
"The text for the right side must not be null!");
this.textRight = textRight;
this.requestLayout();
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
// create the helper layouts if necessary
if (this.layoutLeft == null)
this.layoutLeft = this.makeLayout(this.textLeft);
if (this.layoutRight == null)
this.layoutRight = this.makeLayout(this.textRight);
// find the larger text so both halfs of the switch are equally wide
final int maxTextWidth = Math.max(this.layoutLeft.getWidth(),
this.layoutRight.getWidth());
// calculate the width for the whole switch
int actualWidth = Math.max(
this.switchMinWidth,
maxTextWidth * 2 + this.getPaddingLeft()
+ this.getPaddingRight() + this.innerPadding * 4);
final int switchHeight = Math.max(
this.drawableBackground.getIntrinsicHeight(), // ****Error ON that line Which show the this.drawableBackground is null *******//
this.drawableSwitch.getIntrinsicHeight());// ****Error ON that line Which show the this.drawableSwitch is null *******//
this.width = actualWidth;
this.height = switchHeight;
// recalculate the width if there is a text
if (this.getText() != null)
actualWidth += this.makeLayout(this.getText()).getWidth()
+ this.switchPadding;
// set the dimensions for this view
setMeasuredDimension(actualWidth, switchHeight);
}
@TargetApi(Build.VERSION_CODES.HONEYCOMB_MR2)
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
// Display display = MyService.getScreenWidth(c);
int right;
if (AppConstants.ScreenWidth <= 480) {
right = this.getWidth() - 10;
} else {
right = this.getWidth() - this.getPaddingRight();
}
// Log.e("LOG","width <>" + AppConstants.ScreenWidth);
int left;
if (AppConstants.ScreenWidth <= 480) {
left = right - ((int) (this.width/1.7));
} else {
left = right - this.width;
}
// draw background
this.drawableBackground.setBounds(left, 0, right, this.height);
this.drawableBackground.draw(canvas);
if (AppConstants.ScreenWidth <= 480) {
if (this.isChecked())
this.drawableSwitch.setBounds(left, 0, left
+ ((int) (this.width/3.5)), this.height);
else
this.drawableSwitch.setBounds(left + (int) (this.width/3.5),
0, right, this.height);
} else {
if (this.isChecked())
this.drawableSwitch.setBounds(left, 0, left + (this.width/2),
this.height);
else
this.drawableSwitch.setBounds(left + this.width/2, 0, right,
this.height);
}
this.drawableSwitch.draw(canvas);
// save canvas before translation (0x0)
canvas.save();
if (AppConstants.ScreenWidth <= 480) {
// draw left text
this.getPaint().setColor(
this.isChecked() ? this.textColorChecked
: this.textColorUnChecked);
this.getPaint().setTextSize(17);
canvas.translate(
(float) (left + ((this.width/3.5) - (this.layoutLeft
.getWidth()))/2), (this.height - this.layoutLeft
.getHeight())/2);
this.layoutLeft.draw(canvas);
canvas.restore();
// draw right text
this.getPaint().setColor(
!this.isChecked() ? this.textColorChecked
: this.textColorUnChecked);
this.getPaint().setTextSize(17);
canvas.translate(
(float) (left
+ ((this.width/3.5) - this.layoutRight.getWidth())
/2 + (this.width/3.5)),
(this.height - this.layoutRight.getHeight())/2);
this.layoutRight.draw(canvas);
canvas.restore();
} else {
// draw left text
this.getPaint().setColor(
this.isChecked() ? this.textColorChecked
: this.textColorUnChecked);
canvas.translate(
left + (this.width/2 - this.layoutLeft.getWidth())/2,
(this.height - this.layoutLeft.getHeight())/2);
this.layoutLeft.draw(canvas);
canvas.restore();
// draw right text
this.getPaint().setColor(
!this.isChecked() ? this.textColorChecked
: this.textColorUnChecked);
canvas.translate(
left + (this.width/2 - this.layoutRight.getWidth())/2
+ this.width/2,
(this.height - this.layoutRight.getHeight())/2);
this.layoutRight.draw(canvas);
canvas.restore();
}
}
@Override
public int getCompoundPaddingRight() {
int padding = super.getCompoundPaddingRight() + this.width;
if (!TextUtils.isEmpty(getText()))
padding += this.switchPadding;
return padding;
}
@Override
public void setOnClickListener(OnClickListener l) {
super.setOnClickListener(l);
this.onClickListener = l;
}
@Override
public boolean onTouchEvent(MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
this.performHapticFeedback(HapticFeedbackConstants.VIRTUAL_KEY);
this.setChecked(!this.isChecked());
invalidate();
// call the onClickListener
if (this.onClickListener != null)
this.onClickListener.onClick(this);
return false;
}
return super.onTouchEvent(event);
}
private Layout makeLayout(CharSequence text) {
return new StaticLayout(text, this.getPaint(),
(int) FloatMath.ceil(Layout.getDesiredWidth(text,
this.getPaint())), Layout.Alignment.ALIGN_NORMAL, 1f,
0, true);
}
@Override
protected void drawableStateChanged() {
// TODO don't use the 9-patches directly use a *.xml drawable instead
super.drawableStateChanged();
int[] myDrawableState = getDrawableState();
if (this.drawableSwitch != null)
this.drawableSwitch.setState(myDrawableState);
invalidate();
}
public static class MyService {
public static int getScreenWidth(Activity activity) {
return activity.getWindowManager().getDefaultDisplay().getWidth();
}
}
}
XML
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:background ="@drawable/sectionlist"
xmlns:app="http://schemas.android.com/apk/res/com.example.app"
>
<TextView
android:id="@+id/child_setting_header"
android:layout_width="match_parent"
android:layout_height="60dp"
android:lines="1"
android:layout_toRightOf="@+id/next"
android:gravity="center_vertical"
android:layout_centerVertical="true"
android:layout_gravity="center_vertical"
android:textColor="#FFFFFF"
android:text="Setting"
android:padding="8dp"
android:textSize="@dimen/largexhdpi_menuframe_child_section_textsize"/>
<com.app.widgets.Switch
android:id="@+id/btn_checked_unchecked"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_centerVertical="true"
android:layout_gravity="center_vertical"
android:gravity="right"
app:isChecked="true"
app:textLeft="English"
app:textRight="Hindi"
android:visibility="visible" />
<CheckBox
android:id="@+id/settings_check"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_centerVertical="true"
android:layout_gravity="center_vertical"
android:gravity="right"
android:textColor="@color/menuframe_checkbox_textcolor"
android:visibility="visible" />
錯誤
03-07 12:32:24.141: E/AndroidRuntime(9984): FATAL EXCEPTION: main
03-07 12:32:24.141: E/AndroidRuntime(9984): Process: com.example.app, PID: 9984
03-07 12:32:24.141: E/AndroidRuntime(9984): java.lang.NullPointerException
03-07 12:32:24.141: E/AndroidRuntime(9984): at com.app.widgets.Switch.onMeasure(Switch.java:160)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.view.View.measure(View.java:16458)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:719)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:455)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.view.View.measure(View.java:16458)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.widget.ListView.measureScrapChild(ListView.java:1200)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.widget.ListView.measureHeightOfChildren(ListView.java:1265)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.widget.ListView.onMeasure(ListView.java:1175)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.view.View.measure(View.java:16458)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:666)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.view.View.measure(View.java:16458)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.view.View.measure(View.java:16458)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
03-07 12:32:24.141: E/AndroidRuntime(9984): at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:327)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.view.View.measure(View.java:16458)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
03-07 12:32:24.141: E/AndroidRuntime(9984): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2289)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.view.View.measure(View.java:16458)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1914)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1111)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1293)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:998)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5582)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.view.Choreographer.doCallbacks(Choreographer.java:562)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.view.Choreographer.doFrame(Choreographer.java:532)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.os.Handler.handleCallback(Handler.java:733)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.os.Handler.dispatchMessage(Handler.java:95)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.os.Looper.loop(Looper.java:137)
03-07 12:32:24.141: E/AndroidRuntime(9984): at android.app.ActivityThread.main(ActivityThread.java:4998)
03-07 12:32:24.141: E/AndroidRuntime(9984): at java.lang.reflect.Method.invokeNative(Native Method)
03-07 12:32:24.141: E/AndroidRuntime(9984): at java.lang.reflect.Method.invoke(Method.java:515)
03-07 12:32:24.141: E/AndroidRuntime(9984): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
03-07 12:32:24.141: E/AndroidRuntime(9984): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
03-07 12:32:24.141: E/AndroidRuntime(9984): at dalvik.system.NativeStart.main(Native Method)