Button Android
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Google Android button example source code for developers.
// get handle
Button myButton;
myButton = (Button)findViewById(R.id.idMyButton);
//set focus
myButton.requestFocus();
// set background image
myButton.setBackgroundResource(R.drawable.backImage);
// or
myButton.setBackgroundDrawable(getResources().getDrawable( R.drawable.someImage));
// set visibility
myButton.setVisibility(View.INVISIBLE); // VISIBLE
///////// SET LISTENER
Button myButton =(Button)findViewById(R.id.button1);
myButton.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
Toast.makeText(getApplicationContext(), "AHOJ",
Toast.LENGTH_LONG).show();
}
});
// or set onClickListener
myButton.setOnClickListener(myListener);
//end onCreate .....
private OnClickListener myListener = new OnClickListener() {
public void onClick(View v) {
}
}
397LW NO topic_id
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Activities launcher
public class MainActivity extends ListActivity {
private class Sample {
private CharSequence title;
private Class<? extends Activity> activityClass;
public Sample(int titleResId, Class<? extends Activity> activityClass) {
this.activityClass = activityClass;
this.title = getResources().getString(titleResId);
}
@Override
public String toString() {
return title.toString();
}
}
private static Sample[] mSamples;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Instantiate the list of samples.
mSamples = new Sample[]{
new Sample(R.string.title_first_app, FirstActivity.class),
new Sample(R.string.title_second_app, SecondActivity.class),
new Sample(R.string.title_third_app, ThirdActivity.class),
};
setListAdapter(new ArrayAdapter<Sample>(this,
android.R.layout.simple_list_item_1,
android.R.id.text1,
mSamples));
}
@Override
protected void onListItemClick(ListView listView, View view, int position, long id) {
// Launch the sample associated with this list position.
startActivity(new Intent(MainActivity.this, mSamples[position].activityClass));
}
}
Android development
Java float is 32 bit single precision type and used when fractional precision calculation is required.
Java float je 32 bitů veliké číslo sloužící především pro přesný výsledek za desetinnou tečkou například při dělení čísel. Pro větší přesnost použíijte 64 bitový typ Double.
Java float is 32 bit single precision type and used when fractional precision calculation is required.
Java float je 32 bitů veliké číslo sloužící především pro přesný výsledek za desetinnou tečkou například při dělení čísel. Pro větší přesnost použíijte 64 bitový typ Double.
// declaration and assignment of value type float
float x = 18.41785f;
//print formated value
System.out.printf("The value of x is %.3f%n", x); // 18.418
// declaring more variables in single statement
float f1 = 12.4F, f2 = 564.5F, f3 = 14.589F;
// float range of value
System.out.println(Float.MIN_VALUE); // 4E-45
System.out.println(Float.MAX_VALUE); // 4028235E38
// is NaN Not-a-Number
float f = (float) Math.sqrt(-15);
boolean bNaN = Float.isNaN(f);
System.out.print(bNaN); // true
// check if a string is a valid number in Java example
// convert string to float Java example
String sF = "12.8";
float fParse = Float.parseFloat(sF);
// convert strings to numbers
String sFl = "15.48";
float fFromString = (Float.valueOf(sFl)).floatValue();
// float to string in Java example code
Float fObj = new Float(68.5);
String str = fObj.toString();
// else
Float fS = 11.6f;
String sFloat = fS.toString();
// compare two float variables
Float fComp1 = 4.3f;
if(fComp1.equals(4.3f))
System.out.print("true");
// compares the two specified float values in Java example
int i = Float.compare(11.5f, 11.7f); // -1 first < second
// 0 first == second
// 1 first > second
System.out.print(i);
Converting to string: TypedValue{t=0x10/d=0xe a=-1}
- 14
// error
- "18"
// ok
drawArc(), Canvas, Paint, setStyle()
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new SampleView(this));
}
private static class SampleView extends View {
// CONSTRUCTOR
public SampleView(Context context) {
super(context);
setFocusable(true);
}
@Override
protected void onDraw(Canvas canvas) {
canvas.drawColor(Color.CYAN);
Paint p = new Paint();
// smooths
p.setAntiAlias(true);
p.setColor(Color.RED);
p.setStyle(Paint.Style.STROKE);
p.setStrokeWidth(5);
// opacity
//p.setAlpha(0x80); //
RectF rectF = new RectF(50, 20, 100, 80);
canvas.drawOval(rectF, p);
p.setColor(Color.BLACK);
canvas.drawArc (rectF, 90, 45, true, p);
}
}
}
Problemi is in e.getMessage() what can return null and Log.e (String tag, String msg) will throws an new exception !!!!
Problem and solution:
LogCat:
Or you can using this code:
Problem and solution:
try {
int [] i = {1};
int z = i[5];
} catch (ArrayIndexOutOfBoundsException e) {
String s = e.toString(); // s == java.lang.ArrayIndexOutOfBoundsException
// try to testing String s for null value
if(s != null)
Log.e("bla", s);
else
Log.e("bla", "My error text 1");
String s2 = e.getMessage(); // s2 == null !!!!!!!
// you need to testing String s2 for null value , or you get FATAL EXCEPTION: main
// and application will be crashed
String s2 = e.getMessage(); // s2 == null !!!!!!!
if(s2 != null)
Log.e("bla2", e.getMessage());
else
Log.e("bla2", "My error text 2");
// this is OK
e.printStackTrace();
}
LogCat:
E/bla(855): java.lang.ArrayIndexOutOfBoundsException
E/bla2(855): My error text 2
W/System.err(855): java.lang.ArrayIndexOutOfBoundsException
W/System.err(855): at cz.okhelp.motion._MotionActivity.onTouchEvent(_MotionActivity.java:54)
W/System.err(855): at android.app.Activity.dispatchTouchEvent(Activity.java:2099)
W/System.err(855): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1675)
W/System.err(855): at android.view.ViewRoot.deliverPointerEvent(ViewRoot.java:2194)
W/System.err(855): at android.view.ViewRoot.handleMessage(ViewRoot.java:1878)
W/System.err(855): at android.os.Handler.dispatchMessage(Handler.java:99)
W/System.err(855): at android.os.Looper.loop(Looper.java:123)
W/System.err(855): at android.app.ActivityThread.main(ActivityThread.java:3683)
W/System.err(855): at java.lang.reflect.Method.invokeNative(Native Method)
W/System.err(855): at java.lang.reflect.Method.invoke(Method.java:507)
W/System.err(855): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
W/System.err(855): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
W/System.err(855): at dalvik.system.NativeStart.main(Native Method)
Or you can using this code:
try {
int [] i = {1};
int z = i[5];
} catch (Exception e) {
StringBuilder sb = new StringBuilder().append(e.getClass().getSimpleName());
if (e.getMessage() != null) {
sb.append("
");
sb.append(e.getMessage());
}
Log.e("err", sb.toString()); // E/err(336): ArrayIndexOutOfBoundsException
// this code write out all message
Log.e("myError", "methodName", e);
}
// E/myError(371): methodName
// E/myError(371): java.lang.ArrayIndexOutOfBoundsException
// E/myError(371): at cz.okhelp.motion._MotionActivity.onTouchEvent(_MotionActivity.java:54)
// E/myError(371): at android.app.Activity.dispatchTouchEvent(Activity.java:2099)
// E/myError(371): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1675)
// E/myError(371): at android.view.ViewRoot.deliverPointerEvent(ViewRoot.java:2194)
// E/myError(371): at android.view.ViewRoot.handleMessage(ViewRoot.java:1878)
// E/myError(371): at android.os.Handler.dispatchMessage(Handler.java:99)
// E/myError(371): at android.os.Looper.loop(Looper.java:123)
// E/myError(371): at android.app.ActivityThread.main(ActivityThread.java:3683)
// E/myError(371): at java.lang.reflect.Method.invokeNative(Native Method)
// E/myError(371): at java.lang.reflect.Method.invoke(Method.java:507)
// E/myError(371): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
// E/myError(371): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
// E/myError(371): at dalvik.system.NativeStart.main(Native Method)
Editace: 2011-09-28 07:45:52
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Url:button-android
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