嗨，我是 Android 开发新手......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制。最近几天，我一直被一个特定的问题困扰，似乎无法克服。 用户将输入 2 个值，然后根据这 3 个值进行计算并将其传递给内部类以在图表上绘制。这些值是 TextView 形式的。我知道大部分代码都可以工作，因为我一直在测试它，并且我很确定该错误与 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 错误是:
01-04 13:08:46.764: E/Trace(918): error opening trace file: No such file or directory (2)
01-04 13:08:47.593: D/dalvikvm(918): GC_FOR_ALLOC freed 59K, 3% free 8053K/8259K, paused 105ms, total 108ms
01-04 13:08:47.604: I/dalvikvm-heap(918): Grow heap (frag case) to 8.305MB for 412064-byte allocation
01-04 13:08:47.703: D/dalvikvm(918): GC_FOR_ALLOC freed 1K, 3% free 8454K/8711K, paused 61ms, total 61ms
01-04 13:08:47.764: D/dalvikvm(918): GC_FOR_ALLOC freed 0K, 3% free 8454K/8711K, paused 57ms, total 57ms
01-04 13:08:47.794: I/dalvikvm-heap(918): Grow heap (frag case) to 9.189MB for 928216-byte allocation
01-04 13:08:47.964: D/dalvikvm(918): GC_CONCURRENT freed 0K, 4% free 9361K/9671K, paused 98ms+6ms, total 168ms
01-04 13:08:47.964: D/dalvikvm(918): WAIT_FOR_CONCURRENT_GC blocked 11ms
01-04 13:08:48.344: I/Choreographer(918): Skipped 36 frames! The application may be doing too much work on its main thread.
01-04 13:08:48.374: D/gralloc_goldfish(918): Emulator without GPU emulation detected.
01-04 13:08:50.025: I/Choreographer(918): Skipped 46 frames! The application may be doing too much work on its main thread.
01-04 13:08:56.844: I/Choreographer(918): Skipped 38 frames! The application may be doing too much work on its main thread.
01-04 13:08:57.514: D/AndroidRuntime(918): Shutting down VM
01-04 13:08:57.514: W/dalvikvm(918): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
01-04 13:08:57.614: E/AndroidRuntime(918): FATAL EXCEPTION: main
01-04 13:08:57.614: E/AndroidRuntime(918): java.lang.NullPointerException
01-04 13:08:57.614: E/AndroidRuntime(918): at com.example.ballanimation.calculations$TestA1.onDraw(calculations.java:68)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.View.draw(View.java:13458)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.View.draw(View.java:13342)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.ViewGroup.drawChild(ViewGroup.java:2929)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2799)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.View.draw(View.java:13461)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.widget.FrameLayout.draw(FrameLayout.java:467)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.View.draw(View.java:13342)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.ViewGroup.drawChild(ViewGroup.java:2929)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2799)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.View.draw(View.java:13340)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.ViewGroup.drawChild(ViewGroup.java:2929)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2799)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.View.draw(View.java:13461)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.widget.FrameLayout.draw(FrameLayout.java:467)
01-04 13:08:57.614: E/AndroidRuntime(918): at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:2183)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.ViewRootImpl.drawSoftware(ViewRootImpl.java:2256)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.ViewRootImpl.draw(ViewRootImpl.java:2151)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.ViewRootImpl.performDraw(ViewRootImpl.java:2019)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1830)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:998)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4212)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.Choreographer.doCallbacks(Choreographer.java:555)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.Choreographer.doFrame(Choreographer.java:525)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.os.Handler.handleCallback(Handler.java:615)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.os.Handler.dispatchMessage(Handler.java:92)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.os.Looper.loop(Looper.java:137)
01-04 13:08:57.614: E/AndroidRuntime(918): at android.app.ActivityThread.main(ActivityThread.java:4745)
01-04 13:08:57.614: E/AndroidRuntime(918): at java.lang.reflect.Method.invokeNative(Native Method)
01-04 13:08:57.614: E/AndroidRuntime(918): at java.lang.reflect.Method.invoke(Method.java:511)
01-04 13:08:57.614: E/AndroidRuntime(918): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
01-04 13:08:57.614: E/AndroidRuntime(918): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
01-04 13:08:57.614: E/AndroidRuntime(918): at dalvik.system.NativeStart.main(Native Method)
01-04 13:08:59.854: I/Process(918): Sending signal. PID: 918 SIG: 9
01-04 13:09:13.584: E/Trace(960): error opening trace file: No such file or directory (2)
01-04 13:09:14.364: D/dalvikvm(960): GC_FOR_ALLOC freed 63K, 3% free 8053K/8259K, paused 73ms, total 76ms
01-04 13:09:14.364: I/dalvikvm-heap(960): Grow heap (frag case) to 8.305MB for 412064-byte allocation
01-04 13:09:14.445: D/dalvikvm(960): GC_FOR_ALLOC freed 1K, 3% free 8454K/8711K, paused 42ms, total 42ms
01-04 13:09:14.494: D/dalvikvm(960): GC_FOR_ALLOC freed 0K, 3% free 8454K/8711K, paused 48ms, total 48ms
01-04 13:09:14.514: I/dalvikvm-heap(960): Grow heap (frag case) to 9.189MB for 928216-byte allocation
01-04 13:09:14.684: D/dalvikvm(960): GC_CONCURRENT freed 0K, 4% free 9361K/9671K, paused 80ms+18ms, total 162ms
01-04 13:09:15.024: D/gralloc_goldfish(960): Emulator without GPU emulation detected.
01-04 13:09:16.874: I/Choreographer(960): Skipped 94 frames! The application may be doing too much work on its main thread.
01-04 13:09:20.643: I/Choreographer(960): Skipped 31 frames! The application may be doing too much work on its main thread.
01-04 13:09:32.394: W/ResourceType(960): No package identifier when getting value for resource number 0x00000064
01-04 13:09:32.394: D/AndroidRuntime(960): Shutting down VM
01-04 13:09:32.394: W/dalvikvm(960): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
01-04 13:09:32.454: E/AndroidRuntime(960): FATAL EXCEPTION: main
01-04 13:09:32.454: E/AndroidRuntime(960): android.content.res.Resources$NotFoundException: String resource ID #0x64
01-04 13:09:32.454: E/AndroidRuntime(960): at android.content.res.Resources.getText(Resources.java:229)
01-04 13:09:32.454: E/AndroidRuntime(960): at android.widget.TextView.setText(TextView.java:3620)
01-04 13:09:32.454: E/AndroidRuntime(960): at com.example.ballanimation.calculations$1.onClick(calculations.java:49)
01-04 13:09:32.454: E/AndroidRuntime(960): at android.view.View.performClick(View.java:4084)
01-04 13:09:32.454: E/AndroidRuntime(960): at android.view.View$PerformClick.run(View.java:16966)
01-04 13:09:32.454: E/AndroidRuntime(960): at android.os.Handler.handleCallback(Handler.java:615)
01-04 13:09:32.454: E/AndroidRuntime(960): at android.os.Handler.dispatchMessage(Handler.java:92)
01-04 13:09:32.454: E/AndroidRuntime(960): at android.os.Looper.loop(Looper.java:137)
01-04 13:09:32.454: E/AndroidRuntime(960): at android.app.ActivityThread.main(ActivityThread.java:4745)
01-04 13:09:32.454: E/AndroidRuntime(960): at java.lang.reflect.Method.invokeNative(Native Method)
01-04 13:09:32.454: E/AndroidRuntime(960): at java.lang.reflect.Method.invoke(Method.java:511)
01-04 13:09:32.454: E/AndroidRuntime(960): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
01-04 13:09:32.454: E/AndroidRuntime(960): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
01-04 13:09:32.454: E/AndroidRuntime(960): at dalvik.system.NativeStart.main(Native Method)
01-04 13:09:34.894: I/Process(960): Sending signal. PID: 960 SIG: 9
如果信息量很大，我很抱歉，但我真的被这个问题困扰了。任何帮助将不胜感激。
问候P
最佳答案
因为 View.getText() 永远不会返回 null，只返回 String resultA 、 resultB 或 resultC 可以为 null:
在R.layout内声明了？R.id.result1、R.id.result2、R.id.result3 .calculations_page
关于java - 在类之间传递 TextView 值时出错，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/14158477/