问题
am creating an app in which people can draw a sketch and save to the gallery. This I have done and is working fine. What I would like to be able to do is take an image from the Gallery and be able to draw on that. I have been able to bring up the Gallery to pick the image but I haven't been able to work out how to imbed that image onto the canvas to then draw on
but the prob is , it opens up the gallery...but when i click on any pic to open up, it just goes back to app, but not with the picture, without the picture ( my screen stays same as before, no new picture) ...so what's the problem?
My Mainactivity class---
package com.example.drawingfun;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.InputStream;
import java.util.UUID;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.ImageButton;
import android.widget.LinearLayout;
import android.widget.Toast;
import android.app.AlertDialog;
import android.app.Dialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.view.View.OnClickListener;
public class MainActivity extends Activity implements OnClickListener {
private DrawingView drawView;
private ImageButton currPaint,drawBtn,eraseBtn, newBtn,saveBtn,gal;
private float smallBrush, mediumBrush,largeBrush;
int GALLERY_INTENT_CALLED = 3; // has to be a unique request code
Drawable image;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
drawView = (DrawingView)findViewById(R.id.drawing);
LinearLayout paintLayout = (LinearLayout)findViewById(R.id.paint_colors);
currPaint = (ImageButton)paintLayout.getChildAt(0);
currPaint.setImageDrawable(getResources().getDrawable(R.drawable.paint_pressed));
smallBrush = getResources().getInteger(R.integer.small_size);
mediumBrush = getResources().getInteger(R.integer.medium_size);
largeBrush = getResources().getInteger(R.integer.large_size);
drawBtn = (ImageButton)findViewById(R.id.draw_btn);
drawBtn.setOnClickListener(this);
drawView.setBrushSize(mediumBrush);
eraseBtn = (ImageButton)findViewById(R.id.erase_btn);
eraseBtn.setOnClickListener(this);
newBtn = (ImageButton)findViewById(R.id.new_btn);
newBtn.setOnClickListener(this);
saveBtn = (ImageButton)findViewById(R.id.save_btn);
saveBtn.setOnClickListener(this);
gal = (ImageButton)findViewById(R.id.GalleryButton);
gal.setOnClickListener(this);
}
public void paintClicked(View view){
drawView.setErase(false);
drawView.setBrushSize(drawView.getLastBrushSize());
//use chosen color
if(view!=currPaint){
//update color
ImageButton imgView = (ImageButton)view;
String color = view.getTag().toString();
drawView.setColor(color);
imgView.setImageDrawable(getResources().getDrawable(R.drawable.paint_pressed));
currPaint.setImageDrawable(getResources().getDrawable(R.drawable.paint));
currPaint=(ImageButton)view;
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public void onClick(View view){
//respond to clicks
if(view.getId()==R.id.draw_btn){
//draw button clicked
final Dialog brushDialog = new Dialog(this);
brushDialog.setTitle("Brush size:");
brushDialog.setContentView(R.layout.brush_chooser);
ImageButton smallBtn = (ImageButton)brushDialog.findViewById(R.id.small_brush);
smallBtn.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
drawView.setErase(false);
drawView.setBrushSize(smallBrush);
drawView.setLastBrushSize(smallBrush);
brushDialog.dismiss();
}
});
ImageButton mediumBtn = (ImageButton)brushDialog.findViewById(R.id.medium_brush);
mediumBtn.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
drawView.setErase(false);
drawView.setBrushSize(mediumBrush);
drawView.setLastBrushSize(mediumBrush);
brushDialog.dismiss();
}
});
ImageButton largeBtn = (ImageButton)brushDialog.findViewById(R.id.large_brush);
largeBtn.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
drawView.setErase(false);
drawView.setBrushSize(largeBrush);
drawView.setLastBrushSize(largeBrush);
brushDialog.dismiss();
}
});
brushDialog.show();
}
else if(view.getId()==R.id.erase_btn){
//switch to erase - choose size
final Dialog brushDialog = new Dialog(this);
brushDialog.setTitle("Eraser size:");
brushDialog.setContentView(R.layout.brush_chooser);
ImageButton smallBtn = (ImageButton)brushDialog.findViewById(R.id.small_brush);
smallBtn.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
drawView.setErase(true);
drawView.setBrushSize(smallBrush);
brushDialog.dismiss();
}
});
ImageButton mediumBtn = (ImageButton)brushDialog.findViewById(R.id.medium_brush);
mediumBtn.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
drawView.setErase(true);
drawView.setBrushSize(mediumBrush);
brushDialog.dismiss();
}
});
ImageButton largeBtn = (ImageButton)brushDialog.findViewById(R.id.large_brush);
largeBtn.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
drawView.setErase(true);
drawView.setBrushSize(largeBrush);
brushDialog.dismiss();
}
});
brushDialog.show();
}
else if(view.getId()==R.id.new_btn){
//new button
AlertDialog.Builder newDialog = new AlertDialog.Builder(this);
newDialog.setTitle("New drawing");
newDialog.setMessage("Start new drawing (you will lose the current drawing)?");
newDialog.setPositiveButton("Yes", new DialogInterface.OnClickListener(){
public void onClick(DialogInterface dialog, int which){
drawView.startNew();
dialog.dismiss();
}
});
newDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener(){
public void onClick(DialogInterface dialog, int which){
dialog.cancel();
}
});
newDialog.show();
}
else if(view.getId()==R.id.save_btn){
//save drawing
AlertDialog.Builder saveDialog = new AlertDialog.Builder(this);
saveDialog.setTitle("Save drawing");
saveDialog.setMessage("Save drawing to device Gallery?");
saveDialog.setPositiveButton("Yes", new DialogInterface.OnClickListener(){
public void onClick(DialogInterface dialog, int which){
//save drawing
drawView.setDrawingCacheEnabled(true);
//attempt to save
String imgSaved = MediaStore.Images.Media.insertImage(
getContentResolver(), drawView.getDrawingCache(),
UUID.randomUUID().toString()+".png", "drawing");
//feedback
if(imgSaved!=null){
Toast savedToast = Toast.makeText(getApplicationContext(),
"Drawing saved to Gallery!", Toast.LENGTH_SHORT);
savedToast.show();
}
else{
Toast unsavedToast = Toast.makeText(getApplicationContext(),
"Oops! Image could not be saved.", Toast.LENGTH_SHORT);
unsavedToast.show();
}
drawView.destroyDrawingCache();
}
});
saveDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener(){
public void onClick(DialogInterface dialog, int which){
dialog.cancel();
}
});
saveDialog.show();
}
else if(view.getId()==R.id.GalleryButton){
//new button
AlertDialog.Builder newDialog = new AlertDialog.Builder(this);
newDialog.setTitle("New drawing");
newDialog.setMessage("Start new drawing (you will lose the current drawing)?");
newDialog.setPositiveButton("Yes", new DialogInterface.OnClickListener(){
public void onClick(DialogInterface dialog, int which){
Intent choosePictureIntent = new Intent(
Intent.ACTION_PICK,
android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
startActivityForResult(choosePictureIntent, 101);
}
});
newDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener(){
public void onClick(DialogInterface dialog, int which){
dialog.cancel();
}
});
newDialog.show();
}
}
public void setDrawingThemefrmGallery()
{
Intent pickPhoto = new Intent(
Intent.ACTION_PICK,
android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
startActivityForResult(pickPhoto, GALLERY_INTENT_CALLED);
}
public static Bitmap drawableToBitmap (Drawable drawable) {
if (drawable instanceof BitmapDrawable) {
return ((BitmapDrawable)drawable).getBitmap();
}
Bitmap bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight(), Config.ARGB_8888);
Canvas canvas = new Canvas(bitmap);
drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());
drawable.draw(canvas);
return bitmap;
}
protected void onActivityResult(int requestCode, int resultCode,
Intent returnedIntent) {
drawView.drawImage(drawableToBitmap(image));
super.onActivityResult(requestCode, resultCode, returnedIntent);
if (requestCode == GALLERY_INTENT_CALLED) {
if (resultCode == RESULT_OK) {
try {
Uri selectedImage = returnedIntent.getData();
InputStream inputStream = getContentResolver().openInputStream(selectedImage);
image = Drawable.createFromStream(inputStream, selectedImage.toString());
} catch (FileNotFoundException e) {}
}
}
}
}
My DrawingView class---
package com.example.drawingfun;
import java.io.File;
import android.view.View;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.net.Uri;
import android.provider.MediaStore;
import android.util.AttributeSet;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.CornerPathEffect;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Shader;
import android.view.MotionEvent;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.util.TypedValue;
public class DrawingView extends View {
//drawing path
private Path drawPath;
//drawing and canvas paint
private Paint drawPaint, canvasPaint;
//initial color
private int paintColor = 0xFF660000;
//canvas
private Canvas drawCanvas;
//canvas bitmap
private Bitmap canvasBitmap;
private float brushSize, lastBrushSize;
private boolean erase=false;
public DrawingView(Context context, AttributeSet attrs) {
super(context, attrs);
setupDrawing();
// TODO Auto-generated constructor stub
}
private void setupDrawing() {
// TODO Auto-generated method stub
brushSize = getResources().getInteger(R.integer.medium_size);
lastBrushSize = brushSize;
drawPath = new Path();
drawPaint = new Paint();
drawPaint.setColor(paintColor);
drawPaint.setAntiAlias(true);
drawPaint.setStrokeWidth(brushSize);
drawPaint.setStyle(Paint.Style.FILL_AND_STROKE);
drawPaint.setStrokeJoin(Paint.Join.ROUND);
drawPaint.setStrokeCap(Paint.Cap.ROUND);
canvasPaint = new Paint(Paint.DITHER_FLAG);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
//view given size
super.onSizeChanged(w, h, oldw, oldh);
canvasBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
drawCanvas = new Canvas(canvasBitmap);
}
@Override
protected void onDraw(Canvas canvas) {
//draw view
canvas.drawBitmap(canvasBitmap, 0, 0, canvasPaint);
canvas.drawPath(drawPath, drawPaint);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
//detect user touch
float touchX = event.getX();
float touchY = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
drawPath.moveTo(touchX, touchY);
break;
case MotionEvent.ACTION_MOVE:
drawPath.lineTo(touchX, touchY);
break;
case MotionEvent.ACTION_UP:
drawPath.lineTo(touchX, touchY);
drawCanvas.drawPath(drawPath, drawPaint);
drawPath.reset();
break;
default:
return false;
}
invalidate();
return true;
}
public void setColor(String newColor){
//set color
invalidate();
if(newColor.startsWith("#")){
paintColor = Color.parseColor(newColor);
drawPaint.setColor(paintColor);
drawPaint.setShader(null);
}
else{
//pattern
int patternID = getResources().getIdentifier(
newColor, "drawable", "com.example.drawingfun");
//decode
Bitmap patternBMP = BitmapFactory.decodeResource(getResources(), patternID);
//create shader
BitmapShader patternBMPshader = new BitmapShader(patternBMP,
Shader.TileMode.REPEAT, Shader.TileMode.REPEAT);
//color and shader
drawPaint.setColor(0xFFFFFFFF);
drawPaint.setShader(patternBMPshader);
}
}
public void setBrushSize(float newSize){
//update size
float pixelAmount = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,
newSize, getResources().getDisplayMetrics());
brushSize=pixelAmount;
drawPaint.setStrokeWidth(brushSize);
}
public void setLastBrushSize(float lastSize){
lastBrushSize=lastSize;
}
public float getLastBrushSize(){
return lastBrushSize;
}
public void setErase(boolean isErase){
//set erase true or false
erase=isErase;
if(erase)
{
paintColor = Color.parseColor("WHITE");
drawPaint.setColor(paintColor);
//drawPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
drawPaint.setShader(null);
}
else
drawPaint.setXfermode(null);
}
public void startNew(){
drawCanvas.drawColor(0, PorterDuff.Mode.CLEAR);
invalidate();
}
public void drawImage(Bitmap image) {
drawCanvas.drawBitmap(image, 0, 0, canvasPaint);
invalidate();
}
}
回答1:
You need to load images as Bitmaps and then draw them using a Canvas object.
refer to this question to learn how to convert a drawable to a Bitmap.
And follow this example:
public class DrawView extends View{
private Paint bufferPaint;
private Bitmap buffer;
private Canvas board;
private Path currPath;
public DrawView(Context context) {
super(context);
bufferPaint = new Paint(Paint.DITHER_FLAG);
}
public void init() {
buffer = Bitmap.createBitmap(getWidth(), getHeight(),
Bitmap.Config.ARGB_8888);
board = new Canvas(buffer);
invalidate();
}
public void drawBitmap(Bitmap bitmap) {
board.drawBitmap(bitmap, 0, 0, bufferPaint)
}
@Override
public void onDraw(Canvas canvas) {
if (buffer != null) {
canvas.drawBitmap(buffer, 0, 0, bufferPaint);
}
}
}
the drawBitmap method does the trick. now you can use the canvas object (board) to draw other stuff on your Bitmap.
Define these globally
int GALLERY_INTENT_CALLED = 3; // has to be a unique request code
Drawable image;
Get image from user using this code
Intent pickPhoto = new Intent(
Intent.ACTION_PICK,
android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
startActivityForResult(pickPhoto, GALLERY_INTENT_CALLED);
Then in your activity's onActivityResult, get the image
protected void onActivityResult(int requestCode, int resultCode,
Intent returnedIntent) {
super.onActivityResult(requestCode, resultCode, returnedIntent);
if (requestCode == CAMERA_INTENT_CALLED) {
if (resultCode == RESULT_OK) {
try {
Uri selectedImage = returnedIntent.getData()
InputStream inputStream = getContentResolver().openInputStream(selectedImage);
image = Drawable.createFromStream(inputStream, selectedImage.toString());
} catch (FileNotFoundException e) {}
}
}
}
in DrawingView write this method
public void drawImage(Bitmap image) {
drawCanvas.drawBitmap(image, 0, 0, canvasPaint);
invalidate();
}
use the method from this post to convert image to Bitmap:
public static Bitmap drawableToBitmap (Drawable drawable) {
if (drawable instanceof BitmapDrawable) {
return ((BitmapDrawable)drawable).getBitmap();
}
Bitmap bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight(), Config.ARGB_8888);
Canvas canvas = new Canvas(bitmap);
drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());
drawable.draw(canvas);
return bitmap;
}
then whenever in Mainactivity you wanna draw the image call
drawView.drawImage(drawableToBitmap(image))
来源：https://stackoverflow.com/questions/21764895/how-to-oepn-an-image-to-draw-on-that