double in Java example for Android development
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Java double is 64 bit double precision type used when fractional
precision calculation is required.
Java double je datový typ (reálné číslo) o velikosti 64 bitů. Používá se například pro přesný výsledek po dělení za desetinnou tečkou. Pokud nepotřebuje tak veliké číslo použijte raději typ float, šetříte tím paměť mobilního telefonu.
precision calculation is required.
Java double je datový typ (reálné číslo) o velikosti 64 bitů. Používá se například pro přesný výsledek po dělení za desetinnou tečkou. Pokud nepotřebuje tak veliké číslo použijte raději typ float, šetříte tím paměť mobilního telefonu.
// declaration and assignment of value type double
double x = 18.41785;
//print formated value
System.out.printf("The value of x is %.3f%n", x); // 18.418
// declaring more variables in single statement
double d1 = 12.4, d2 = 564.5, d3 = 14.589;
// double range of value
System.out.println(Double.MIN_VALUE); // 4.9E-324
System.out.println(Double.MAX_VALUE); // 1.7976931348623157E308
// is NaN Not-a-Number
double f = (double) Math.sqrt(-15);
boolean bNaN = Double.isNaN(f);
System.out.print(bNaN); // true
// check if a string is a valid number in Java example
// convert string to double Java example
String sD = "12.8";
double dParse = Double.parseDouble(sD);
// convert strings to numbers
String sDl = "15.48";
double dFromString = (Double.valueOf(sDl)).doubleValue();
// format double, float or long value to string
DecimalFormat formatter = new DecimalFormat(".##");
String s = formatter.format(-.5678); // -0.57
// .### -0.568
// .#### -0.5678
// .000000 -.567800
// -123.456
// .## -123.46
// #.## -123.46
// #E0 -.1E3
// ##E0 -1.2E2
//###E0 -123E0
// double to string in Java example code
Double dObj = new Double(68.5);
String str = dObj.toString();
// else
Double dS = 11.6;
String sdouble = dS.toString();
// compare two double variables
Double dComp1 = 4.3;
if(dComp1.equals(4.3))
System.out.print("true");
// compares the two specified double values in Java example
// int i = compare(double d1, double d2);
int i = Double.compare(11.5, 11.7); // -1 first < second
// 0 first == second
// 1 first > second
System.out.print(i);
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Další témata ....(Topics)
Spinner, ArrayAdapter, setOnItemSelectedListener, onItemSelected, setDropDownViewResource
MainClass.java
strings.xml
MainClass.java
public class Vypocet extends Activity {
Spinner hSpinnerMetry;
// .......
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
hSpinnerMetry = (Spinner) findViewById(R.id.idSpinnerMetry);
ArrayAdapter<CharSequence> adapterMetry = ArrayAdapter.createFromResource(
this, R.array.metry_array, android.R.layout.simple_spinner_item);
adapterMetry.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
hSpinnerMetry.setAdapter(adapterMetry);
hSpinnerMetry.setOnItemSelectedListener(
new OnItemSelectedListener() {
public void onItemSelected(
AdapterView<?> parent, View view, int position, long id) {
int nPos = position;
}
public void onNothingSelected(AdapterView<?> parent) {
}
});
}
}
strings.xml
<string-array name="metry_array">
<item>m</item>
<item>dm</item>
<item>cm</item>
<item>mm</item>
</string-array>
onCreate in MainActivity.java
You can add to titlebar different Views by xml file.
custom_title.xml
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_CUSTOM_TITLE);
setContentView(R.layout.main.xml);
getWindow().setFeatureInt(Window.FEATURE_CUSTOM_TITLE, R.layout.custom_title);
}
You can add to titlebar different Views by xml file.
custom_title.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="//schemas.android.com/apk/res/android" android:id="@+id/screen"
android:layout_width="fill_parent" android:layout_height="fill_parent"
android:orientation="vertical">
<TextView android:id="@+id/left_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:text="Some text" />
<ImageView
android:id="@+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_alignParentRight="true"
android:src="@drawable/ic_launcher" />
</RelativeLayout>
Dialog Yes No sample code
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage("Are you sure you want to exit application?")
.setCancelable(false)
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
MyActivity.this.finish(); //Close this Activity for example: MyActivity.java
}
})
.setNegativeButton("No", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
// some code if you want
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
If I create own folder layout-w320dp with Eclipse Android 4.4
layout was correctly loaded.
If I trying this application on tablet with Android 2.1 application crashed.
layout was correctly loaded.
If I trying this application on tablet with Android 2.1 application crashed.
private int[] mData = new int[2]; // fill some values into array!!
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putBoolean("myBoolean", true);
outState.putDouble("myDouble", 2.7);
outState.putInt("myInt", 5);
outState.putString("myString", "Heloo girls!");
int[] data = new int[mData.length];
for (int i = 0; i < data.length; i++) {
data[i] = mData[i];
}
outState.putIntArray("myArray", data);
}
@Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
boolean myBoolean = savedInstanceState.getBoolean("myBoolean", false); // false basic value
double myDouble = savedInstanceState.getDouble("myDouble", 1.5); // 1.5 basic value
int myInt = savedInstanceState.getInt("myInt", 10);
String myString = savedInstanceState.getString("myString", "Hello boys!");
int[] data = savedInstanceState.getIntArray("myArray");
if (data != null && data.length == mData.length) {
for (int i = 0; i < data.length; i++) {
mData[i] = data[i];
}
}
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
boolean myBoolean = savedInstanceState != null ? savedInstanceState.getBoolean("myBoolean", false) : true;
// etc. .......
}
Editace: 2011-09-26 20:49:42
Počet článků v kategorii: 396
Url:double-in-java-example-for-android-development
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