java - 将 imageview 设置为图像导致崩溃

Question

当我尝试设置任何 imageview 图像(setImageBitmap 或 setImageView)时， Activity 崩溃，它会在除一个 getview 之外的任何地方执行此操作。

我正在尝试获取一个可以在我的 gridview 适配器中使用的 imageview 数组(问题标记为“此处问题”)

package joshpike.hsh.hsh_game;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Point;
import android.os.Bundle;
import android.view.Display;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.view.WindowManager;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;


public class DisplayActivity extends MainActivity
{

    int screenTileWidth = 3;
    int nativeTileSize = 256;
    int tileSize;
    int numberColumn;
    int numberRow;
    int floorNum;

    ImageView[][] topGridArray = null;
    ImageView[][] bottomGridArray = null;

    //sets tilesize, numberColumn and numberRow
    @SuppressLint("NewApi")
    public void setGridVars()
    {
        //set tileSize 
        Display display = getWindowManager().getDefaultDisplay();
        Point size = new Point();
        int screenWidth;

        if (android.os.Build.VERSION.SDK_INT >= 13)
        {
            display.getSize(size);
            screenWidth = size.x;
        }
        else
        {
            screenWidth = display.getWidth();
        }

        tileSize = screenWidth / screenTileWidth;

        //set numberColumn and numberRow
        try
        {
            String dataFilePath = "floors/" + floorNum + "/FloorData.txt";
            InputStream dataInputStream = getAssets().open(dataFilePath);
            BufferedReader reader = new BufferedReader(new InputStreamReader(dataInputStream));

            String line = reader.readLine();
            line = reader.readLine();
            numberColumn = Integer.parseInt(line);
            line = reader.readLine();
            numberRow = Integer.parseInt(line);
            dataInputStream.close();
        }
        catch (IOException e) 
        {
            System.out.println("exception found in try/catch in DisplayActivity.setGridVars method");
        }

        for(int x = 0; x < numberColumn ; x++ )
        {
            for(int y = 0; y < numberRow ; y++ )
            {
                ///***PROBLEM HERE***///
                bottomGridArray[x][y].setImageBitmap(currentImageView("bottom", x, y));
                topGridArray[x][y].setImageBitmap(currentImageView("top", x, y));
            }
        }




    }

    //returns the one imageView for gridViewForadapter 
    public Bitmap currentImageView(String layer, int X, int Y ) 
    {
        try 
        {
            Bitmap returnBitmap = null;
            String imgDirectory = "floors/" + floorNum + "/" + layer + "/" + X + "," + Y + ".png";

            InputStream imageInputStream = getAssets().open(imgDirectory);
            returnBitmap = BitmapFactory.decodeStream(imageInputStream);
            imageInputStream.close();
            return returnBitmap;

        } 
        catch (IOException e) 
        {
            System.out.println("exception found in try/catch in DisplayActivity.currentImageView method");
            return null;
        }

    }


    public int returnGridCord (int position, char whatCord)
    {
        position = position + 1;

        float rowFromTop = (float)  position / numberColumn;

        if (rowFromTop != Math.round(rowFromTop))
        {
            rowFromTop = ((float) Math.ceil( rowFromTop));
        }

        int returnY = Math.abs( (int)rowFromTop - numberRow);
        int returnX = (position - ( ( (int)rowFromTop -1 ) * numberColumn) ) - 1;

        System.out.println(position + ":" + returnX + "x" + returnY);
        if (whatCord == 'X')
        {
            return returnX;
        }
        else
        {
            return returnY;
        }
    }


    public class ImageAdapter extends BaseAdapter 
    {

        private Context mContext;

        // create a new ImageView for each item referenced by the Adapter
        public View getView(int position, View convertView, ViewGroup parent) 
        {
            ImageView imageView;
            if (convertView == null) 
            {  
                // if it's not recycled, initialize some attributes
                imageView = new ImageView(mContext);
                imageView.setLayoutParams(new GridView.LayoutParams(tileSize, tileSize));
                imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
                imageView.setPadding(0, 0, 0, 0);
            } 
            else 
            {
                imageView = (ImageView) convertView;
            }




            System.out.println("endish of getview");    

            imageView.setImageResource(R.drawable.ic_launcher);
            return imageView;

        }


        public ImageAdapter(Context c) 
        {
            mContext = c;
        }

        @Override
        public int getCount() 
        {
            return numberColumn * numberRow;
        }

        @Override
        public Object getItem(int position) 
        {
            return null;
        }

        @Override
        public long getItemId(int position) 
        {
            return 0;
        }

    }




    // Inflate the menu; this adds items to the action bar if it is present.
    //makes the options menu
    @Override
    public boolean onCreateOptionsMenu(Menu menu) 
    {
        getMenuInflater().inflate(R.menu.display, menu);
        return true;
    }

    //what happens if you select items from the options menu
    @Override
    public boolean onOptionsItemSelected(MenuItem item)
    {
        switch (item.getItemId() )
        {
            case R.id.miniMap:

            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    //called when activity is started for first time either for first time or after destoryed
    @Override
    protected void onCreate(Bundle savedInstanceState) 
    {
        this.requestWindowFeature(Window.FEATURE_NO_TITLE);
        this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
        super.onCreate(savedInstanceState);
        setContentView(R.layout.display);
        setGridVars();





        System.out.println("DisplayActivity test about to start");     
        //ImageAdapter test = null;
        //returnGridCord(0,"X");




        GridView bottomMapGrid = (GridView)findViewById(R.id.bottomMapGrid);
        bottomMapGrid.setNumColumns(numberColumn); 
        bottomMapGrid.setColumnWidth( tileSize );
        bottomMapGrid.setStretchMode( GridView.NO_STRETCH ) ;   
        bottomMapGrid.setAdapter(new ImageAdapter(this));

        System.out.println("DisplayActivity onCreate done");        
    }



    //called when Activity goes from paused to active
    @Override
    protected void onResume()
    {
        super.onResume();
        System.out.println("DisplayActivity onResume done");
    }

    //called when Activity goes from active to paused
    @Override
    protected void onPause()
    {
        super.onPause();
        System.out.println("DisplayActivity onPause done");

    }

    //called when Activity goes from paused to stopped
    @Override
    protected void onStop()
    {
        super.onStop();
        System.out.println("DisplayActivity onStop done");

    }

    //called when Activity goes from stopped to destroyed
    @Override
    protected void onDestroy()
    {
        super.onDestroy();
        System.out.println("DisplayActivity onDestroy done");

    }

    //called when Activity has been stopped, is going to be paused then active
    @Override
    protected void onRestart()
    {
        super.onRestart();
        System.out.println("DisplayActivity onRestart done");

    }

    //called when Activity is transitioning to paused either for first time or after it has been stopped
    @Override
    protected void onStart()
    {
        super.onStart();
        System.out.println("DisplayActivity onStart done");

    }

}

日志猫:

03-20 17:16:43.437: I/System.out(22850): MainActivity onCreate done
03-20 17:16:43.437: I/System.out(22850): MainActivity onStart done
03-20 17:16:43.437: I/System.out(22850): MainActivity onResume done
03-20 17:16:43.848: D/TextLayoutCache(22850): Using debug level: 0 - Debug Enabled: 0
03-20 17:16:44.088: D/libEGL(22850): loaded /system/lib/egl/libGLES_android.so
03-20 17:16:44.168: D/libEGL(22850): loaded /system/lib/egl/libEGL_mali.so
03-20 17:16:44.208: D/libEGL(22850): loaded /system/lib/egl/libGLESv1_CM_mali.so
03-20 17:16:44.218: D/libEGL(22850): loaded /system/lib/egl/libGLESv2_mali.so
03-20 17:16:44.358: D/OpenGLRenderer(22850): Enabling debug mode 0
03-20 17:16:48.973: I/System.out(22850): MainActivity onPause done
03-20 17:16:49.974: D/OpenGLRenderer(22850): Flushing caches (mode 0)
03-20 17:16:50.674: I/System.out(22850): MainActivity onCreate done
03-20 17:16:50.915: D/AndroidRuntime(22850): Shutting down VM
03-20 17:16:50.915: W/dalvikvm(22850): threadid=1: thread exiting with uncaught exception (group=0x40aa8210)
03-20 17:16:51.005: E/AndroidRuntime(22850): FATAL EXCEPTION: main
03-20 17:16:51.005: E/AndroidRuntime(22850): java.lang.RuntimeException: Unable to start activity ComponentInfo{joshpike.hsh.hsh_game/joshpike.hsh.hsh_game.DisplayActivity}: java.lang.NullPointerException
03-20 17:16:51.005: E/AndroidRuntime(22850):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1967)
03-20 17:16:51.005: E/AndroidRuntime(22850):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1992)
03-20 17:16:51.005: E/AndroidRuntime(22850):    at android.app.ActivityThread.access$600(ActivityThread.java:127)
03-20 17:16:51.005: E/AndroidRuntime(22850):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1158)
03-20 17:16:51.005: E/AndroidRuntime(22850):    at android.os.Handler.dispatchMessage(Handler.java:99)
03-20 17:16:51.005: E/AndroidRuntime(22850):    at android.os.Looper.loop(Looper.java:137)
03-20 17:16:51.005: E/AndroidRuntime(22850):    at android.app.ActivityThread.main(ActivityThread.java:4448)
03-20 17:16:51.005: E/AndroidRuntime(22850):    at java.lang.reflect.Method.invokeNative(Native Method)
03-20 17:16:51.005: E/AndroidRuntime(22850):    at java.lang.reflect.Method.invoke(Method.java:511)
03-20 17:16:51.005: E/AndroidRuntime(22850):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:823)
03-20 17:16:51.005: E/AndroidRuntime(22850):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:590)
03-20 17:16:51.005: E/AndroidRuntime(22850):    at dalvik.system.NativeStart.main(Native Method)
03-20 17:16:51.005: E/AndroidRuntime(22850): Caused by: java.lang.NullPointerException
03-20 17:16:51.005: E/AndroidRuntime(22850):    at joshpike.hsh.hsh_game.DisplayActivity.setGridVars(DisplayActivity.java:85)
03-20 17:16:51.005: E/AndroidRuntime(22850):    at joshpike.hsh.hsh_game.DisplayActivity.onCreate(DisplayActivity.java:235)
03-20 17:16:51.005: E/AndroidRuntime(22850):    at android.app.Activity.performCreate(Activity.java:4465)
03-20 17:16:51.005: E/AndroidRuntime(22850):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
03-20 17:16:51.005: E/AndroidRuntime(22850):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1931)
03-20 17:16:51.005: E/AndroidRuntime(22850):    ... 11 more
03-20 17:16:56.510: I/Process(22850): Sending signal. PID: 22850 SIG: 9

Answer 1

你永远不会初始化bottomGridArray。就此而言，topGridArray 也不是。 (查看this topic in a basic Java tutorial to see how and why you need to initialize your arrays)

在你的行之前

for(int x = 0; x < numberColumn ; x++ )
    {
        for(int y = 0; y < numberRow ; y++ )

插入

bottomGridArray = new ImageGrid[numberColumn][numberRow];
topGridArray = new ImageGrid[numberColumn][numberRow];

请注意:您的代码可能会遇到很多麻烦。您可能应该看看 Google 对 Bitmaps in your UI 的建议.