我在运行时使用onClickListeners创建了一些textViews。
但是我得到了NullPointer..。我认为原因是View，他不知道textView应该在哪里。
我该如何解决？
该课程的有趣之处ShowSomething：
textView.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(ShowSomething.this, textView.getText().toString(), Toast.LENGTH_LONG).show();
}
});
layout.addView(t);
全班ShowSomething：
public class ShowSomething extends Activity {
public void showData(final String[][] array, final int i, int j, LinearLayout layout, final TextView t, TextView t2, int color) {
String Text = null;
int size = 12;
int top = 0;
int bot = 0;
if (j == 0) {
size = 14;
Text = array[j][i];
top = 5;
bot = 0;
}
if (j == 1) {
size = 10;
Text = " " + array[j][i];
top = 5;
bot = 5;
}
t.setTextSize(TypedValue.COMPLEX_UNIT_DIP, size);
t.setTextColor(color);
t.setPadding(0, top, 0, bot);
t.setClickable(false);
t.setText(Text);
t.setId(j + i);
t.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(ShowSomething.this, t.getText().toString(), Toast.LENGTH_LONG).show();
}
});
layout.addView(t);
}
}
该课程的有趣之处ProjectsActivity：
setContentView(R.layout.activity_projects);
int j = 0;
//result
for (i = 0; i < array[0].length; i++) {
while (j <2) {
LinearLayout layout = (LinearLayout) findViewById(R.id.mainLayout);
final TextView t = new TextView(getApplicationContext());
final TextView t2 = new TextView(getApplicationContext());
ShowSomething.showData(array, i, j, layout, t, t2, color);
全班ProjectsActivity：
public class ProjectsActivity extends Activity {
public String[][] array = null;
public int i = 0;
int color;
ShowSomething show = new ShowSomething();
@SuppressLint("NewApi")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_projects);
int j = 0;
array = Connect.printJobList();
for (i = 0; i < array[0].length; i++) {
while (j < 2) {
LinearLayout layout = (LinearLayout) findViewById(R.id.mainLayout);
final TextView t = new TextView(getApplicationContext());
final TextView t2 = new TextView(getApplicationContext());
if (j == 0){
color = getResources().getColor(R.color.Project1);
}
if (j == 1){
color = getResources().getColor(R.color.Project2);
}
show.showData(array, i, j, layout, t, t2, color);
if (j == 1){
t2.setLayoutParams(new LinearLayout.LayoutParams(LayoutParams.MATCH_PARENT, 1));
t2.setBackgroundColor(getResources().getColor(R.color.Line));
layout.addView(t2);
}
j++;
}
j = 0;
}
}
}
LogCat：
03-26 08:19:38.294: D/AndroidRuntime(1991): Shutting down VM
03-26 08:19:38.294: W/dalvikvm(1991): threadid=1: thread exiting with uncaught exception (group=0x414c4700)
03-26 08:19:38.332: E/AndroidRuntime(1991): FATAL EXCEPTION: main
03-26 08:19:38.332: E/AndroidRuntime(1991): java.lang.NullPointerException
03-26 08:19:38.332: E/AndroidRuntime(1991): at android.app.Activity.setContentView(Activity.java:1895)
03-26 08:19:38.332: E/AndroidRuntime(1991): at de.xcom.mobilenav.ShowSomething$1.onClick(ShowSomething.java:47)
03-26 08:19:38.332: E/AndroidRuntime(1991): at android.view.View.performClick(View.java:4240)
03-26 08:19:38.332: E/AndroidRuntime(1991): at android.view.View$PerformClick.run(View.java:17721)
03-26 08:19:38.332: E/AndroidRuntime(1991): at android.os.Handler.handleCallback(Handler.java:730)
03-26 08:19:38.332: E/AndroidRuntime(1991): at android.os.Handler.dispatchMessage(Handler.java:92)
03-26 08:19:38.332: E/AndroidRuntime(1991): at android.os.Looper.loop(Looper.java:137)
03-26 08:19:38.332: E/AndroidRuntime(1991): at android.app.ActivityThread.main(ActivityThread.java:5103)
03-26 08:19:38.332: E/AndroidRuntime(1991): at java.lang.reflect.Method.invokeNative(Native Method)
03-26 08:19:38.332: E/AndroidRuntime(1991): at java.lang.reflect.Method.invoke(Method.java:525)
03-26 08:19:38.332: E/AndroidRuntime(1991): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
03-26 08:19:38.332: E/AndroidRuntime(1991): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
03-26 08:19:38.332: E/AndroidRuntime(1991): at dalvik.system.NativeStart.main(Native Method)
第47行ShowSomething：（忽略评论）
43 public void onClick(View v) {
44 //Intent intent = new Intent(ShowSomething.this, ProjectDetailActivity.class);
45 //intent.putExtra("Project", array[0][i]);
46
47 //startActivity(intent);
48
49 Toast.makeText(ShowSomething.this, t.getText().toString(), Toast.LENGTH_LONG).show();
更改了班级ShowSomething：
public class ShowSomething {
.
.
. t.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(ShowSomething.this, ProjectDetailActivity.class);
intent.putExtra("Project", array[0][i]);
startActivity(intent);
//Toast.makeText(getApplicationContext() , t.getText().toString(), Toast.LENGTH_LONG).show();
}
});
但是现在我得到一个错误：构造函数Intent（ShowSomething，Class）是未定义的...
可能您的上下文有问题，.makeText的第一个参数。您需要检查在哪条线中有NPE。查看LogCat窗口，您将看到类似以下内容：
由以下原因引起的：packagename.ShowSomething.showData（ShowSomething.java:123）上的java.lang.NullPointerException
然后，您将知道在哪里拥有NPE，或者只是进一步询问。
编辑后：
因此，您正在尝试在任何上下文中立即启动Intent（ShowSomething目前尚未扩展活动）
您需要将Context传递给ShowSomething类（可能是在构造函数中），然后使用它：
public class ShowSomething {
...
Context mContext;
public ShowSomething(Context context){
this.mContext=context;
}
调用：mContext.startActivity（intent）; 在onClickListener中
然后在您的主要活动中创建ShowSomething对象：
ShowSomething myClass = new ShowSomething（getApplicationContext（））;
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