如何在“自定义视图”中调用设置更改通过从按钮调用函数。？

Question

我创建了一个自定义视图组件，我的布局文件由一个按钮和 CustomView 组成。每当我按下按钮时，我想更新 CustomView 类中的文件名。这是通过调用 set_file 方法来实现的customview 和 set_file 方法在函数 perform(); 中调用。但是，这样做时出现错误。

这是我的 3 节课。

TestActivity.java

包 com.android.pack;

导入 java.net.URISyntaxException;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup.LayoutParams;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.Toast;

    public class TestActivity extends Activity {
    /** Called when the activity is first created. */
    int height;
    int weight;
    Button select;
    customview cView;
    String path="";
        String pathchk="";
        String temp="";

     private static final int FILE_SELECT_CODE = 0;

        public void perform()
        {
            cView.set_file(pathchk);
            cView.postInvalidate();
        }
         public void showFileChooser(View v) {
            Intent intent = new Intent(Intent.ACTION_GET_CONTENT); 
            intent.setType("*/*"); 
            intent.addCategory(Intent.CATEGORY_OPENABLE);

            try {
                startActivityForResult(
                        Intent.createChooser(intent, "Select a File to Upload"),
                        FILE_SELECT_CODE);

            } catch (android.content.ActivityNotFoundException ex) {
                // Potentially direct the user to the Market with a Dialog
                Toast.makeText(this, "Please install a File Manager.", 
                        Toast.LENGTH_SHORT).show();
            }
        }
     protected void onActivityResult(int requestCode, int resultCode, Intent data)
     {
            switch (requestCode) {
                case FILE_SELECT_CODE:      
                if (resultCode == RESULT_OK) {  
                    // Get the Uri of the selected file 
                    Uri uri = data.getData();
                    Log.v("check", "File Uri: " + uri.toString());
                    // Get the path

                    try {
                        path = FileUtils.getPath(this, uri);
                        pathchk=path.substring(12);
                        perform();



                    } catch (URISyntaxException e) {
                        // TODO Auto-generated catch block
                        Log.v("error", "File Path: "+pathchk);
                    }
                    Log.v("check", "File Path: "+path);
                    // Get the file instance
                    // File file = new File(path);
                    // Initiate the upload
                }           
                break;
            }
        super.onActivityResult(requestCode, resultCode, data);
        }
    @Override

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        LayoutInflater li = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View v=li.inflate(R.layout.main, null);
        cView = (customview)findViewById(R.id.customview1);

       LinearLayout ll = new LinearLayout(this);
        ll.setOrientation(LinearLayout.VERTICAL);
        select=(Button)findViewById(R.id.button1);
       // select.setText("Select a File");
       /* select.setOnClickListener(new Button.OnClickListener(){

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                showFileChooser();
                Toast.makeText(getApplicationContext(), "The File "+path+" is loaded",Toast.LENGTH_LONG);           }





               }); */


       // LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(
          //  LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);




        //ll.addView(select, new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));

       //ll.addView(cView, layoutParams);

        setContentView(R.layout.main); 



    }
}

customview.java

package com.android.pack;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.StringTokenizer;

import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.gesture.Gesture;
import android.gesture.GesturePoint;
import android.gesture.GestureStroke;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Point;
import android.os.Environment;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
import android.view.View.*
;
import android.widget.Button;
import android.widget.Toast;

public class customview extends View implements OnClickListener 
{
    ArrayList<GesturePoint> child;
    ArrayList<Point> pnts;
    Point pnt=new Point();
     File myFile;
     BufferedReader br;
     FileInputStream in;
     InputStreamReader fin;
     GestureStroke gest;
     Gesture my_final=new Gesture();
     String Token;
     long Time=30000000;
     int flag=0; 
     boolean line=true;
     boolean points=true;
     Button b1;
     int height;
     int weight;
     String Filename="";

     ArrayList<Path> paths;

     Path mypath;
     Paint mypaint=new Paint();//
     public void set_file(String a)// to set the File
     {
         Filename=a;
         //clear_screen();
     }
     public customview(Context context)
     {
         super(context);
         this.setOnClickListener(this);
         mypaint.setColor(Color.RED);
         mypaint.setAntiAlias(true);
         mypaint.setStyle(Paint.Style.STROKE);
         mypaint.setStrokeWidth(5);
         myFile=Environment.getExternalStorageDirectory();

     }
     public customview(Context context,AttributeSet att)
     {
         super(context,att);
         this.setOnClickListener(this);
         mypaint.setColor(Color.RED);
         mypaint.setAntiAlias(true);
         mypaint.setStyle(Paint.Style.STROKE);
         mypaint.setStrokeWidth(5);
         myFile=Environment.getExternalStorageDirectory();
     }
     public void make_shape()
    {
        paths=new ArrayList<Path>();
        pnts=new ArrayList<Point>();
        height=this.getHeight();
        weight=this.getWidth();
        Log.v("Main_custom_height",height+"");
        Log.v("Main_custom_weight",weight+"");
          try
          {
            File file = new File(myFile,Filename);
            br=new BufferedReader(new FileReader(file));

            String read;
            while((read=br.readLine())!=null)
            {

                //Toast.makeText(Create_pathActivity.this,read,Toast.LENGTH_SHORT).show();
                if(read.equals(".PEN_UP"))
                {
                    flag=0;
                    gest=new GestureStroke(child);
                    mypath=gest.getPath();
                    paths.add(mypath);
                    my_final.addStroke(gest);

                }
                if(flag==1)
                {
                    StringTokenizer st = new StringTokenizer(read);
                         for(int i=0;i<=2;i++)
                         {
                             if(i==0)
                             {
                                 Token=st.nextToken();
                                 pnt.x=Integer.parseInt(Token);
                                 //pnt.x=pnt.x+200;
                                 //pnt.x=pnt.x/5;

                                 Log.v("PointX",Token);
                             }
                             if(i==1)
                             {
                                 Token=st.nextToken();
                                 pnt.y=Integer.parseInt(Token);
                                 //pnt.y=pnt.y+165;
                                 //pnt.y=pnt.y/5;
                                 Log.v("PointY",Token);
                             }
                             if(i==2)
                             {

                                 Time=Time+10;
                                 GesturePoint temp=new GesturePoint(pnt.x,pnt.y,Time);
                                 child.add(temp);
                             }

                        }
                         Point p=new Point();
                         p.x=pnt.x;
                         p.y=pnt.y;
                         pnts.add(p);


                }
                if(read.equals(".PEN_DOWN"))
                {
                    flag=1;
                    child=new ArrayList<GesturePoint>();
                }
            }

        }catch (Exception e)
        {


        }
    }


    protected void onDraw(Canvas canvas)
    {
        if(points==true && line==false)
        {

                for (Point point : pnts) {
                    canvas.drawCircle(point.x, point.y, 3,mypaint);
                }   

        }
        if(points==false && line==true)
        {
                            for( int i=0;i<paths.size();i++)
                {
                    canvas.drawPath(paths.get(i), mypaint);
                }

        }

    }
    public void scale()
    {
        int S_width = 320, S_height = 410, width, height, DiffW, DiffH;
          int max_x = 0, max_y = 0, min_x = 320, min_y = 410;
          int new_x, new_y;
          int i;
          float scale;


          for(i=0; i<pnts.size(); i++)
          {
            if( pnts.get(i).x > max_x )
                max_x = pnts.get(i).x;

            if( pnts.get(i).x < min_x )
                min_x = pnts.get(i).x;

            if( pnts.get(i).y > max_y )
                max_y = pnts.get(i).y;

            if( pnts.get(i).y < min_y )
                min_y = pnts.get(i).y;

          }

            width = max_x - min_x;
            height = max_y - min_y;

            DiffW = Math.abs(S_width - width);
            DiffH = Math.abs(S_height - height);

            if( DiffW > DiffH )
                scale = width/300;
            else
                scale = height/390;

            //scaling
            for(i=0; i<pnts.size(); i++)
            {
                pnts.get(i).x /= scale;
                pnts.get(i).y /= scale;
            }

            new_x = max_x - 10;
            new_y = min_y - 10;

            //top-left shifting
            for(i=0; i<pnts.size(); i++)
            {
                pnts.get(i).x -= new_x;
                pnts.get(i).y -= new_y;
            }

    }



    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        if(Filename.equals(""))
        {
            Toast.makeText(getContext(),"Select a file ist", Toast.LENGTH_SHORT);
            return;
        }
        make_shape();

        AlertDialog.Builder builder = new AlertDialog.Builder(getContext());
        builder.setCancelable(true);
        builder.setTitle("Draw a line or a path");
        builder.setInverseBackgroundForced(true);
        builder.setPositiveButton("Line", new DialogInterface.OnClickListener() {
         @Override
        public void onClick(DialogInterface dialog, int which) {
            line=true;
            points=false;
            invalidate();
              }
        });
        builder.setNegativeButton("Point", new DialogInterface.OnClickListener() {
          @Override
         public void onClick(DialogInterface dialog, int which) {
       line=false;
       points=true;
       //scale();
       invalidate();
          }
        });
        AlertDialog alert = builder.create();
        alert.show();


    }


}

**FileUtils.java**


package com.android.pack;

import java.net.URISyntaxException;

import android.content.Context;
import android.database.Cursor;
import android.net.Uri;

public class FileUtils {

    public static String getPath(Context context, Uri uri) throws URISyntaxException {
        if ("content".equalsIgnoreCase(uri.getScheme())) {
            String[] projection = { "_data" };
            Cursor cursor = null;

            try {
                cursor = context.getContentResolver().query(uri, projection, null, null, null);
                int column_index = cursor
                .getColumnIndexOrThrow("_data");
                if (cursor.moveToFirst()) {
                    return cursor.getString(column_index);
                }
            } catch (Exception e) {
                // Eat it
            }
        }

        else if ("file".equalsIgnoreCase(uri.getScheme())) {
            return uri.getPath();
        }

        return null;
    }
}

这是我的 ma​​in.xml 文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

     <com.android.pack.customview
        android:id="@+id/customview1"
        android:layout_width="wrap_content"
        android:layout_height="419dp"
        android:layout_weight="0.63"
       />


    <Button
        android:id="@+id/button1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="select a file" 
        android:onClick="showFileChooser"/>

</LinearLayout>

我的日志猫是

01-09 12:04:42.038: D/szipinf(4990): Initializing inflate state
01-09 12:04:42.248: D/dalvikvm(4990): GC_CONCURRENT freed 281K, 50% free 2860K/5639K, external 0K/0K, paused 4ms+8ms
01-09 12:04:48.668: V/check(4990): File Uri: content://org.openintents.cmfilemanager/mimetype//mnt/sdcard/points.txt
01-09 12:04:48.698: D/AndroidRuntime(4990): Shutting down VM
01-09 12:04:48.698: W/dalvikvm(4990): threadid=1: thread exiting with uncaught exception (group=0x40018560)
01-09 12:04:48.698: E/AndroidRuntime(4990): FATAL EXCEPTION: main
01-09 12:04:48.698: E/AndroidRuntime(4990): java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=0, result=-1, data=Intent { act=android.intent.action.VIEW dat=content://org.openintents.cmfilemanager/mimetype//mnt/sdcard/points.txt }} to activity {com.android.pack/com.android.pack.TestActivity}: java.lang.NullPointerException
01-09 12:04:48.698: E/AndroidRuntime(4990):     at android.app.ActivityThread.deliverResults(ActivityThread.java:2653)
01-09 12:04:48.698: E/AndroidRuntime(4990):     at android.app.ActivityThread.handleSendResult(ActivityThread.java:2695)
01-09 12:04:48.698: E/AndroidRuntime(4990):     at android.app.ActivityThread.access$2000(ActivityThread.java:123)
01-09 12:04:48.698: E/AndroidRuntime(4990):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:969)
01-09 12:04:48.698: E/AndroidRuntime(4990):     at android.os.Handler.dispatchMessage(Handler.java:99)
01-09 12:04:48.698: E/AndroidRuntime(4990):     at android.os.Looper.loop(Looper.java:130)
01-09 12:04:48.698: E/AndroidRuntime(4990):     at android.app.ActivityThread.main(ActivityThread.java:3835)
01-09 12:04:48.698: E/AndroidRuntime(4990):     at java.lang.reflect.Method.invokeNative(Native Method)
01-09 12:04:48.698: E/AndroidRuntime(4990):     at java.lang.reflect.Method.invoke(Method.java:507)
01-09 12:04:48.698: E/AndroidRuntime(4990):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:847)
01-09 12:04:48.698: E/AndroidRuntime(4990):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:605)
01-09 12:04:48.698: E/AndroidRuntime(4990):     at dalvik.system.NativeStart.main(Native Method)
01-09 12:04:48.698: E/AndroidRuntime(4990): Caused by: java.lang.NullPointerException
01-09 12:04:48.698: E/AndroidRuntime(4990):     at com.android.pack.TestActivity.perform(TestActivity.java:32)
01-09 12:04:48.698: E/AndroidRuntime(4990):     at com.android.pack.TestActivity.onActivityResult(TestActivity.java:64)
01-09 12:04:48.698: E/AndroidRuntime(4990):     at android.app.Activity.dispatchActivityResult(Activity.java:3908)
01-09 12:04:48.698: E/AndroidRuntime(4990):     at android.app.ActivityThread.deliverResults(ActivityThread.java:2649)
01-09 12:04:48.698: E/AndroidRuntime(4990):     ... 11 more

感谢任何帮助！！

Answer 1

尝试放在

setContentView(R.layout.main)

supr.onCreate之后而不是最后。

super.onCreate(savedInstanceState);
setContentView(R.layout.main);

Answer 2

你还没有完成SetcontentView来调用findviewby id。你必须打电话

cView = (customview)v.findViewById(R.id.customview1);

Answer 3

You are trying to add button and layouts before setting its Layout main 
change

setContentView(R.layout.main)
before
    LayoutInflater li = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View v=li.inflate(R.layout.main, null);
        cView = (customview)findViewById(R.id.customview1);

       LinearLayout ll = new LinearLayout(this);
        ll.setOrientation(LinearLayout.VERTICAL);
        select=(Button)findViewById(R.id.button1);