Java 传递TextView值时出错

几天前我问了这个问题，但我刚刚意识到我包含了错误的logcat错误，现在包含了正确的logcat

我正在编写一个应用程序，允许用户输入值，并将它们用于在图表上绘图。最近几天，我遇到了一个特别的问题，似乎无法克服。用户将输入2个值，并从这3个值中计算并传递给要绘制在图表上的内部类。这些值是文本视图形式的。我知道大部分代码在测试时都能正常工作，我很确定错误与TextView值有关。下面是用于计算和绘制图表的代码

package com.example.ballanimation;

import java.math.BigDecimal;

import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.RectF;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class calculations extends Activity {

EditText firstVal, secondVal;
TextView resultA, resultB, resultC;
Button button3;
BigDecimal firstNum, secNum;

@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.calculations_page);

button3 = (Button) findViewById(R.id.button3);

firstVal = (EditText) findViewById(R.id.editTXT1);
secondVal = (EditText) findViewById(R.id.editTXT2);

resultA = (TextView) findViewById(R.id.result1);
resultB = (TextView) findViewById(R.id.result2);
resultC = (TextView) findViewById(R.id.result3);


button3.setOnClickListener(new View.OnClickListener() {

    public void onClick(View v) {
        // TODO Auto-generated method stub
        firstNum = new BigDecimal(firstVal.getText().toString());
        secNum = new BigDecimal(secondVal.getText().toString());
        resultA.setText(firstNum.add(secNum).toString());
        resultB.setText(firstNum.subtract(secNum).toString());
        resultC.setText(firstNum.multiply(secNum).toString());

    }
});


}

class TestA1 extends View{

public TestA1(Context context) {
    super(context);
    // TODO Auto-generated constructor stub
}

public void onDraw(Canvas canvas){
    super.onDraw(canvas);

    String TestA = resultA.getText().toString();
    String TestB = resultB.getText().toString();
    String TestC = resultC.getText().toString();

    int A = Integer.parseInt(TestA);
    int B = Integer.parseInt(TestB);
    int C = Integer.parseInt(TestC);

    Paint red = new Paint();
    red.setColor(Color.RED);
    red.setStyle(Paint.Style.STROKE);

    Paint black = new Paint();
    black.setColor(Color.BLACK);
    black.setStyle(Paint.Style.STROKE);

    canvas.drawCircle(A, B, C, black);
    canvas.drawCircle(canvas.getWidth()*1/2, canvas.getHeight()*3/8,    canvas.getWidth()*475/1000, black);
    canvas.drawCircle(canvas.getWidth()*5/8, canvas.getWidth()*5/8, canvas.getWidth()*349/1000, black);
    canvas.drawCircle(canvas.getWidth()*6/8, canvas.getWidth()*5/8, canvas.getWidth()*228/1000, black);
    canvas.drawCircle(canvas.getWidth()*7/8, canvas.getWidth()*5/8, canvas.getWidth()*103/1000, black);

    canvas.drawLine((canvas.getWidth()-canvas.getWidth()) + 10, (canvas.getHeight()*3)/8, canvas.getWidth() - 10, (canvas.getHeight()*3)/8, black);

    float a, b, c, d, e, f, g, h, i, j, k, l;

    a = 90;   //degrees
    b = 90;
    c = 90;
    d = 50;
    e = 90;
    f = 134;
    g = -90;
    h = -90;
    i = -90;
    j = -50;
    k = -90;
    l = -134;

    RectF arc0 = new RectF();
    RectF arc1 = new RectF();
    RectF arc2 = new RectF();
    RectF arc3 = new RectF();
    RectF arc4 = new RectF();
    RectF arc5 = new RectF();

    /*left  The X coordinate of the left side of the rectangle 
    top  The Y coordinate of the top of the rectangle 
    right  The X coordinate of the right side of the rectangle 
    bottom  The Y coordinate of the bottom of the rectangle  */



    arc0.set(canvas.getWidth()*1/2, canvas.getHeight()*-139/700, canvas.getWidth()*100/69, canvas.getHeight()*3/8); 
    arc1.set(canvas.getWidth()*-6/112, canvas.getHeight()*-80/100, canvas.getWidth()*195/100, canvas.getHeight()*72/192);   
    arc2.set(canvas.getWidth()*7/10, canvas.getHeight()*70/700, canvas.getWidth()*125/100, canvas.getHeight()*3/8); 
    arc3.set(canvas.getWidth()/2, canvas.getHeight()*3/8, canvas.getWidth()*100/69, canvas.getHeight()*91/96);
    arc4.set(canvas.getWidth()*-8/112, canvas.getHeight()*3/8, canvas.getWidth()*195/100, canvas.getHeight()*150/100);
    arc5.set(canvas.getWidth()*7/10, canvas.getHeight()*3/8, canvas.getWidth()*125/100, canvas.getHeight()*65/100);


    /*oval  The bounds of oval used to define the shape and size of the arc 
    startAngle  Starting angle (in degrees) where the arc begins 
    sweepAngle  Sweep angle (in degrees) measured clockwise 
    useCenter  If true, include the center of the oval in the arc, and close it if it is being stroked. This will draw a wedge 
    paint  The paint used to draw the arc  */

    canvas.drawArc(arc0, a, b, false, red);
    canvas.drawArc(arc1, c, d, false, red);
    canvas.drawArc(arc2, e, f, false, red);
    canvas.drawArc(arc3, g, h, false, red);
    canvas.drawArc(arc4, i, j, false, red);
    canvas.drawArc(arc5, k, l, false, red);

}
}
}

我收到的Logcat错误有：

01-08 11:54:05.436: D/dalvikvm(714): GC_FOR_ALLOC freed 42K, 3% free 8053K/8259K, paused 66ms, total 69ms
01-08 11:54:05.436: I/dalvikvm-heap(714): Grow heap (frag case) to 8.305MB for 412064-byte allocation
01-08 11:54:05.596: D/dalvikvm(714): GC_FOR_ALLOC freed 1K, 3% free 8455K/8711K, paused 55ms, total 55ms
01-08 11:54:05.647: D/dalvikvm(714): GC_FOR_ALLOC freed 0K, 3% free 8455K/8711K, paused 48ms, total 48ms
01-08 11:54:05.666: I/dalvikvm-heap(714): Grow heap (frag case) to 9.189MB for 928216-byte allocation
01-08 11:54:05.836: D/dalvikvm(714): GC_CONCURRENT freed 0K, 4% free 9361K/9671K, paused 98ms+9ms, total 173ms
01-08 11:54:05.836: D/dalvikvm(714): WAIT_FOR_CONCURRENT_GC blocked 3ms
01-08 11:54:06.186: D/gralloc_goldfish(714): Emulator without GPU emulation detected.
01-08 11:54:07.856: I/Choreographer(714): Skipped 79 frames!  The application may be doing too much work on its main thread.
01-08 11:54:25.786: D/AndroidRuntime(714): Shutting down VM
01-08 11:54:25.816: W/dalvikvm(714): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
01-08 11:54:25.866: E/AndroidRuntime(714): FATAL EXCEPTION: main
01-08 11:54:25.866: E/AndroidRuntime(714): java.lang.NullPointerException
01-08 11:54:25.866: E/AndroidRuntime(714):  at com.example.ballanimation.calculations$TestA1.onDraw(calculations.java:83)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.View.draw(View.java:13458)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.View.draw(View.java:13342)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.ViewGroup.drawChild(ViewGroup.java:2929)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2799)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.View.draw(View.java:13461)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.widget.FrameLayout.draw(FrameLayout.java:467)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.View.draw(View.java:13342)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.ViewGroup.drawChild(ViewGroup.java:2929)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2799)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.View.draw(View.java:13340)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.ViewGroup.drawChild(ViewGroup.java:2929)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2799)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.View.draw(View.java:13461)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.widget.FrameLayout.draw(FrameLayout.java:467)
01-08 11:54:25.866: E/AndroidRuntime(714):  at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:2183)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.ViewRootImpl.drawSoftware(ViewRootImpl.java:2256)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.ViewRootImpl.draw(ViewRootImpl.java:2151)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.ViewRootImpl.performDraw(ViewRootImpl.java:2019)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1830)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:998)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4212)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.Choreographer.doCallbacks(Choreographer.java:555)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.Choreographer.doFrame(Choreographer.java:525)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.os.Handler.handleCallback(Handler.java:615)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.os.Handler.dispatchMessage(Handler.java:92)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.os.Looper.loop(Looper.java:137)
01-08 11:54:25.866: E/AndroidRuntime(714):  at android.app.ActivityThread.main(ActivityThread.java:4745)
01-08 11:54:25.866: E/AndroidRuntime(714):  at java.lang.reflect.Method.invokeNative(Native Method)
01-08 11:54:25.866: E/AndroidRuntime(714):  at java.lang.reflect.Method.invoke(Method.java:511)
01-08 11:54:25.866: E/AndroidRuntime(714):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
01-08 11:54:25.866: E/AndroidRuntime(714):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
01-08 11:54:25.866: E/AndroidRuntime(714):  at dalvik.system.NativeStart.main(Native Method)
01-08 11:54:28.535: I/Process(714): Sending signal. PID: 714 SIG: 9

我很确定该错误包含在以下行中：

                    String TestA = resultA.getText().toString();
        String TestB = resultB.getText().toString();
        String TestC = resultC.getText().toString();

我传递TextView值的方式一定有问题，但我看不出问题出在哪里

任何帮助都将不胜感激。

您的类名“calculations”以小写字母开头，并假设它应该以大写字母“C”开头

将此代码放在TestA1类之外，并在类内使用此变量。 您完成了。希望它能有所帮助。

尝试以下方法：

        String TestA="",TestB="",TestC="";

        if(!resultA.getText().toString().equals("")) 
            TestA = resultA.getText().toString();
        if(!resultB.getText().toString().equals("")) 
            TestB = resultB.getText().toString();
        if(!resultC.getText().toString().equals("")) 
            TestC = resultC.getText().toString();

而不是：

        String TestA = resultA.getText().toString();
        String TestB = resultB.getText().toString();
        String TestC = resultC.getText().toString();

---

谢谢。

大家好，这里有两个可能导致NullPointerException的原因

1） 首先，文本视图中的字符串可能没有输入和

2） 其次，各个文本视图的id（

R.id.result1、R.id.result2、R.id.result3

）可能不在活动中使用的同一版面（

R.layout.calculations\u page

）中

对于第一个场景，您可以按照Pratik Sharma的建议进行操作

第二次检查空

resultA、resultB、resultC

e、 g

---

NullPointerException 01-08 11:54:25.866:E/AndroidRuntime（714）：在com.example.ballanimation.calculations$TestA1.onDraw（calculations.java:83）

哪一行是onDraw（）函数的第83行？@这一行中包含的内容

calculations.java:83

？@PratikSharma hi感谢您的回复，第83行包含：字符串TestA=resultA.getText（）.toString（）；字符串TestB=resultB.getText（）.toString（）；字符串TestC=resultC.getText（）.toString（）@好的。尝试我在下面发布的解决方案。@user1927105您的问题解决了吗？我想这应该是一个评论。但我同意你的看法。

        String TestA = resultA.getText().toString();
        String TestB = resultB.getText().toString();
        String TestC = resultC.getText().toString();

if(resultA!=null){
}