How to draw a line in android

Question

Can anybody tell how to  draw a line in Android  perhaps with an example

User · Answer

canvas drawLine 10  10  90  10  paint   canvas drawLine 10  20  90  20  paint     This will create a straight horizontal line  hope it helps

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You can draw multiple straight lines on view using  Finger paint example which is in Developer android   example link  Just comment  mPath quadTo mX  mY   x   mX  2   y   mY  2   You will be able to draw straight lines   import android app Activity  import android content Context  import android graphics Bitmap  import android graphics Canvas  import android graphics Color  import android graphics Paint  import android graphics Path  import android graphics Point  import android os Bundle  import android view MotionEvent  import android view View  import android view View OnTouchListener  import android widget ImageView   public class JoinPointsActivity extends Activity            Called when the activity is first created         Paint mPaint      float Mx1 My1      float x y       Override      public void onCreate Bundle savedInstanceState            super onCreate savedInstanceState             setContentView R layout main           MyView view1  new MyView this           view1 setBackgroundResource R drawable image 0031 layer 1           setContentView view1             mPaint   new Paint            mPaint setAntiAlias true           mPaint setDither true           mPaint setColor 0xFFFF0000           mPaint setStyle Paint Style STROKE           mPaint setStrokeJoin Paint Join ROUND             mPaint setStrokeCap Paint Cap ROUND           mPaint setStrokeWidth 10               public class MyView extends View            private static final float MINP   0 25f          private static final float MAXP   0 75f         private Bitmap  mBitmap          private Canvas  mCanvas          private Path    mPath         private Paint   mBitmapPaint           public MyView Context c                super c                mPath   new Path              mBitmapPaint   new Paint Paint DITHER FLAG                       Override        protected void onSizeChanged int w  int h  int oldw  int oldh                super onSizeChanged w  h  oldw  oldh               mBitmap   Bitmap createBitmap w  h  Bitmap Config ARGB 8888               mCanvas   new Canvas mBitmap                       Override         protected void onDraw Canvas canvas                canvas drawColor 0xFFAAAAAA                 canvas drawLine mX  mY  Mx1  My1  mPaint                 canvas drawLine mX  mY  x  y  mPaint               canvas drawBitmap mBitmap  0  0  mBitmapPaint               canvas drawPath mPath  mPaint                       private float mX  mY          private static final float TOUCH TOLERANCE   4           private void touch start float x  float y                mPath reset                mPath moveTo x  y               mX   x              mY   y                    private void touch move float x  float y                float dx   Math abs x - mX               float dy   Math abs y - mY               if  dx  gt   TOUCH TOLERANCE    dy  gt   TOUCH TOLERANCE                      mPath quadTo mX  mY   x   mX  2   y   mY  2                   mX   x                  mY   y                                  private void touch up                 mPath lineTo mX  mY                  commit the path to our offscreen             mCanvas drawPath mPath  mPaint                  kill this so we don t double draw             mPath reset                        Override         public boolean onTouchEvent MotionEvent event                float x   event getX                float y   event getY                 switch  event getAction                      case MotionEvent ACTION DOWN                      touch start x  y                       invalidate                        break                  case MotionEvent ACTION MOVE                      touch move x  y                       invalidate                        break                  case MotionEvent ACTION UP                      touch up                        Mx1  int  event getX                         My1   int  event getY                       invalidate                        break                            return true

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package com example helloandroid   import android app Activity  import android content Context  import android graphics Canvas  import android graphics Color  import android graphics Paint  import android os Bundle  import android view View   public class HelloAndroid2Activity extends Activity           Called when the activity is first created     DrawView drawView    Override public void onCreate Bundle savedInstanceState        super onCreate savedInstanceState        drawView   new DrawView this       drawView setBackgroundColor Color WHITE       setContentView drawView     class DrawView extends View           Paint paint   new Paint             public DrawView Context context                super context               paint setColor Color BLUE                      Override         public void onDraw Canvas canvas                 super onDraw canvas                   canvas drawLine 10  20  30  40  paint                   canvas drawLine 20  10  50  20  paint

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There are two main ways you can draw a line  by using a Canvas or by using a View   Drawing a Line with Canvas  From the documentation we see that we need to use the following method   drawLine  float startX  float startY  float stopX  float stopY  Paint paint    Here is a picture     The Paint object just tells Canvas what color to paint the line  how wide it should be  and so on   Here is some sample code   private Paint paint   new Paint          private void init         paint setColor Color BLACK       paint setStrokeWidth 1f       Override protected void onDraw Canvas canvas        super onDraw canvas        startX   20      startY   100      stopX   140      stopY   30       canvas drawLine startX  startY  stopX  stopY  paint       Drawing a Line with View  If you only need a straight horizontal or vertical line  then the easiest way may be to just use a View in your xml layout file  You would do something like this    lt View     android layout width  match parent      android layout height  1dp      android background   android color black    gt    Here is a picture with two lines  one horizontal and one vertical  to show what it would look like     And here is the complete xml layout for that    lt  xml version  1 0  encoding  utf-8   gt   lt LinearLayout xmlns android  http   schemas android com apk res android  android layout width  match parent  android layout height  match parent  android orientation  vertical   gt    lt TextView     android layout width  match parent      android layout height  wrap content      android padding  10dp      android text  TextView1 in vertical linear layout    gt    lt View     android layout width  match parent      android layout height  1dp      android background   android color black    gt    lt TextView     android layout width  match parent      android layout height  wrap content      android padding  10dp      android text  TextView2 in vertical linear layout    gt    lt LinearLayout     android layout width  match parent      android layout height  wrap content   gt        lt TextView         android layout width  100dp          android layout height  100dp          android padding  10dp          android text  TextView3 in horizontal linear layout    gt        lt View         android layout width  1dp          android layout height  match parent          android background   android color black    gt        lt TextView         android layout width  100dp          android layout height  100dp          android padding  10dp          android text  TextView4 in horizontal linear layout    gt   lt  LinearLayout gt    lt  LinearLayout gt

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this code adds horizontal line to a linear layout  View view   new View this   LinearLayout LayoutParams lpView   new LinearLayout LayoutParams LinearLayout LayoutParams MATCH PARENT  1      -- gt  horizontal view setLayoutParams lpView   view setBackgroundColor Color DKGRAY    linearLayout addView view

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for horizontal line on the layout      lt View             android id    id View03              android layout width  fill parent              android layout height  5dip              android background   0f0    gt    for vertical line on the layout     lt View         android id    id View04          android layout width  5dip          android layout height  fill parent          android background   0f0    gt

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Another approach to draw a line programatically using ImageView  import android app Activity  import android graphics Bitmap  import android graphics Canvas  import android graphics Color  import android graphics Paint  import android graphics Path  import android graphics Typeface  import android os Bundle  import android widget ImageView   public class Test extends Activity     ImageView drawingImageView      Override   public void onCreate Bundle savedInstanceState        super onCreate savedInstanceState       setContentView R layout main       drawingImageView    ImageView  this findViewById R id DrawingImageView       Bitmap bitmap   Bitmap createBitmap  int  getWindowManager            getDefaultDisplay   getWidth     int  getWindowManager            getDefaultDisplay   getHeight    Bitmap Config ARGB 8888       Canvas canvas   new Canvas bitmap       drawingImageView setImageBitmap bitmap           Line     Paint paint   new Paint        paint setColor Color GREEN       paint setStrokeWidth 10       int startx   50      int starty   100      int endx   150      int endy   210      canvas drawLine startx  starty  endx  endy  paint

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This one draws 2 lines which form a cross on the top left of the screen    DrawView java  import android content Context  import android graphics Canvas  import android graphics Color  import android graphics Paint  import android view View   public class DrawView extends View       Paint paint   new Paint         private void init             paint setColor Color BLACK              public DrawView Context context            super context           init               public DrawView Context context  AttributeSet attrs            super context  attrs           init               public DrawView Context context  AttributeSet attrs  int defStyle            super context  attrs  defStyle           init                Override     public void onDraw Canvas canvas                canvas drawLine 0  0  20  20  paint               canvas drawLine 20  0  0  20  paint              The activity to start it   StartDraw java  import android app Activity  import android graphics Color  import android os Bundle   public class StartDraw extends Activity       DrawView drawView        Override     public void onCreate Bundle savedInstanceState            super onCreate savedInstanceState            drawView   new DrawView this           drawView setBackgroundColor Color WHITE           setContentView drawView

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If you re working with ConstraintLayout you need to define at least 2 constraints for the line to show up  Like this    lt View         android layout width  0dp          android layout height  1dp          android background   android color black          app layout constraintEnd toEndOf    id someView1          app layout constraintStart toStartOf    id someView2          app layout constraintTop toBottomOf    id someView3    gt    Though I defined 3 constraints

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or if you just want a line  TextView line   new TextView this               line setBackgroundResource android R color holo red dark               line setHeight  int  Utility convertDpToPixel 1 this

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To improve on the answers provided by  Janusz  I added this to my styles    lt style name  Divider  gt       lt item name  android layout width  gt match parent lt  item gt       lt item name  android layout height  gt 1dp lt  item gt       lt item name  android background  gt  android attr listDivider lt  item gt   lt  style gt    Then in my layouts is less code and simpler to read    lt View style   style Divider   gt    if you want to do horizontal line spacing then do the above      And for vertical line between two Views you have to replace android layout width parameters attributes  with android layout height

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Simple one    lt TextView     android layout width  match parent      android layout height  1dp      android background   c0c0c0      android id    id your id      android layout marginTop  160dp    gt

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If you want to have a simple Line in your Layout to separate two views you can use a generic View with the height and width you want the line to have and a set background color     With this approach you don t need to override a View or use a Canvas yourself just simple and clean add the line in xml     lt View  android layout width  match parent   android layout height  1dp   android background   android color black    gt    The example code I provided will generate a line that fills the screen in width and has a height of one dp     If you have problems with the drawing of the line on small screens consider to change the height of the line to px  The problem is that on a ldpi screen the line will be 0 75 pixel high  Sometimes this may result in a rounding that makes the line vanish  If this is a problem for your layout define the width of the line a ressource file and create a separate ressource file for small screens that sets the value to 1px instead of 1dp   This approach is only usable if you want horizontal or vertical lines that are used to divide layout elements  If you want to achieve something like a cross that is drawn into an image my approach will not work

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final SurfaceView surf    SurfaceView findViewById R id surface home                   surf setOnTouchListener  new SurfaceView OnTouchListener                        private boolean moving   false   stupid state                     public boolean onTouch View v  MotionEvent event                            switch  event getAction                              case MotionEvent ACTION DOWN                              final int x    int event getX                                final int y    int event getY                                final Rect bounds   mTiles getBounds                                moving   bounds intersects x  y  x 1  y 1                               return true                          case MotionEvent ACTION MOVE                              if  moving                                    final int x new    int event getX                                    final int y new    int event getY                                    mDrawTiles draw  new DrawLogic                                        public void draw Rect  surface                                            mTiles setBounds                                              x new - mDrawWidth 2                                              y new - mDrawHeight 2                                              x new   mDrawWidth 2                                              y new   mDrawHeight 2

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You can make a drawable like circle  line  rectangle etc through shapes in xml as follow    lt  xml version  1 0  encoding  utf-8   gt   lt shape xmlns android  http   schemas android com apk res android       android shape  line   gt        lt solid android color   00000000    gt        lt stroke         android width  2dp          android color   808080    gt    lt  shape gt

[android] How to draw a line in android

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