float in Java example code
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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);
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String s = "AbcČ";
String s2 = s.toLowerCase(new Locale("cs_CZ")); // Czech Republic
String s3 = s.toLowerCase(new Locale("de_DE")); // Germany
//
en_US
en_GB
ar_EG
be_BY
bg_BG
ca_ES
cs_CZ
da_DK
de_DE
"id cannot be resolved or is not a field” error
If you copy project to workspace or some code from other project you can get this error.
Try remove or add import your R file:
Check xml files.
Clean project by menu Project-Clean
Maybe you have to create new project end copy old source files to new project folders.
If you copy project to workspace or some code from other project you can get this error.
Try remove or add import your R file:
import com.example.app.R
Check xml files.
Clean project by menu Project-Clean
Maybe you have to create new project end copy old source files to new project folders.
drawPath, canvas.rotate, lineTo basic Android example for your testing.
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// //www.apache.org/licenses/LICENSE-2.0
// The Android Open Source Project
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new SampleView(this));
}
private static class SampleView extends View {
private Paint mPaint = new Paint();
private Path mPath = new Path();
// CONSTRUCTOR
public SampleView(Context context) {
super(context);
setFocusable(true);
// Construct a wedge-shaped path
mPath.moveTo(0, -60);
mPath.lineTo(-20, 80);
mPath.lineTo(0, 60);
mPath.lineTo(20, 80);
mPath.close();
}
@Override
protected void onDraw(Canvas canvas) {
Paint paint = mPaint;
canvas.drawColor(Color.WHITE);
paint.setAntiAlias(true);
paint.setColor(Color.RED);
paint.setStyle(Paint.Style.FILL);
Bitmap bitmapOrg = BitmapFactory.decodeResource(getResources(),
R.drawable.flower_blue);
canvas.drawBitmap(bitmapOrg, 10, 10, paint);
int w = canvas.getWidth();
int h = canvas.getHeight();
int cx = w / 2;
int cy = h / 2;
canvas.translate(cx, cy);
// uncomment next line
//canvas.rotate(90.0f);
canvas.drawPath(mPath, mPaint);
}
}
}
If You have old PC (Android in emulator with high screen resolution uses a lot of memory) or your testing phone have small screen, You can try this trick.
Rename layout folder for small device screen f.g. from layout into layout-swXXXdp and a large layout-sw600dp into layout.
Your phone with small screnn will do select xml file from renamed layout folder (for small screen).
You can to testing rotation with device en stability of fragments if an application changed orientation.
If you have old pc, you can try to make a new virtual device running on older version of Android, which uses less memory of computer.
For testing of rotation stability - application orientation changed - use on emulator Ctrl+F11, Ctrl+F12 key (Windows).
Important
Before the release of application, you have to rename layout folder to older name layout-sw600dp and layout-swXXXdp to layout.
Rename layout folder for small device screen f.g. from layout into layout-swXXXdp and a large layout-sw600dp into layout.
Your phone with small screnn will do select xml file from renamed layout folder (for small screen).
You can to testing rotation with device en stability of fragments if an application changed orientation.
If you have old pc, you can try to make a new virtual device running on older version of Android, which uses less memory of computer.
For testing of rotation stability - application orientation changed - use on emulator Ctrl+F11, Ctrl+F12 key (Windows).
Important
Before the release of application, you have to rename layout folder to older name layout-sw600dp and layout-swXXXdp to layout.
How to change the image dynamically in ImageView and button setOnClickListener Android sample.
Main.java
main.xml
Put into res/drawable this pictures:
Main.java
ipackage cz.okhelp.my_game;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
public class Main extends Activity {
private ImageView hImageViewSemafor;
private Button hButton;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
hImageViewSemafor = (ImageView)findViewById(R.id.idImageViewSemafor);
hButton = (Button) findViewById(R.id.idBtnChangeImage);
hButton.setOnClickListener(mButtonChangeImageListener);
}
View.OnClickListener mButtonChangeImageListener = new OnClickListener() {
public void onClick(View v) {
// setImageResource will change image in ImageView
hImageViewSemafor.setImageResource(R.drawable.semafor_green);
}
};
}
main.xml
Put into res/drawable this pictures:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="//schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/hello"
/>
<ImageView
android:src="@drawable/semafor_red"
android:id="@+id/idImageViewSemafor"
android:background="#66FFFFFF"
android:adjustViewBounds="true"
android:maxWidth="47dip"
android:maxHeight="91dip"
android:padding="10dip"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
Editace: 2011-09-26 20:49:50
Počet článků v kategorii: 397
Url:float-in-java-example-code
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