Question

如何在适配器中启动活动？我在我的适配器中使用此方法：

post.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        context.startActivity(new Intent(context,asabani_cat.class));
    }
});

但这只适用于我的应用程序的片段，当我在Activity App中调用此代码时突然崩溃了！

我有另一个问题，是在适配器中启动活动的好方法吗？

我的logcat：

11-27 21：25：25.086 22237-22237 / com.katibehpayam.mahdi.katibehpayam E / AndroidRuntime：致命例外：主要11-27 21：25：25.086 22237-22237 / com.katibehpayam.mahdi.katibehpayam E / AndroidRuntime：java.lang.NullPointerException 11-27 21:25:25.086 22237-22237 / com.katibehpayam.mahdi.katibehpayam E / AndroidRuntime：at com.katibehpayam.mahdi.katibehpayam.adapter_common $ 7.onClick（adapter_common.java:266 ）11-27 21：25：25.086 22237-22237 / com.katibehpayam.mahdi.katibehpayam E / AndroidRuntime：at android.view.View.performClick（View.java:4377)11-27 21:25:25.086 22237-22237 /com.katibehpayam.mahdi.katibehpayam E / AndroidRuntime：在android.view.View $ PerformClick.run（View.java:18044)11-27 21:25:25.086 22237-22237 / com.katibehpayam.mahdi.katibehpayam E / AndroidRuntime：在android.os.Handler.handleCallback（Handler.java:725)11-27 21:25:25.086 22237-22237 / com.katibehpayam.mahdi.katibehpayam E / AndroidRuntime：at android.os.Handler.dispatchMessage（Handler .java：92）11-27 21：25：25.086 22237-22237 / com.katibehpay am.mahdi.katibehpayam E / AndroidRuntime：在android.os.Looper.loop（Looper.java:137)11-27 21:25:25.086 22237-22237 / com.katibehpayam.mahdi.katibehpayam E / AndroidRuntime：在android。 app.ActivityThread.main（ActivityThread.java:5306)11-27 21:25:25.086 22237-22237 / com.katibehpayam.mahdi.katibehpayam E / AndroidRuntime：at java.lang.reflect.Method.invokeNative（Native Method）11 -27 21：25：25.086 22237-22237 / com.katibehpayam.mahdi.katibehpayam E / AndroidRuntime：at java.lang.reflect.Method.invoke（Method.java:511)11-27 21:25:25.086 22237-22237 /com.katibehpayam.mahdi.katibehpayam E / AndroidRuntime：at com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:1102)11-27 21:25:25.086 22237-22237 / com.katibehpayam.mahdi .katibehpayam E / AndroidRuntime：at com.android.internal.os.ZygoteInit.main（ZygoteInit.java:869)11-27 21:25:25.086 22237-22237 / com.katibehpayam.mahdi.katibehpayam E / AndroidRuntime：at dalvik .system.NativeStart.main（原生方法）

Answer 1

你可以尝试：

# install.packages("ggplot2", dependencies = TRUE)
require(ggplot2)

df <- structure(list(Sample = structure(1:12, .Label = c("sample1_A", 
"Sample1_B", "sample2_A", "sample2_B", "sample3_A", "sample3_B", 
"sample4_A", "sample4_B", "sample5_A", "sample5_B", "sample6_A", 
"sample6_B"), class = "factor"), observation1 = c(163453473L, 
170151351L, 194102849L, 170642240L, 192858504L, 177174787L, 199232380L, 
211128931L, 186039420L, 145855252L, 211165202L, 220522502L), 
    observation2 = c(131232689L, 137202212L, 162112484L, 141888123L, 
    161227348L, 147412720L, 174656081L, 186848929L, 152618196L, 
    118225865L, 186625116L, 193191927L), observation3 = c(61984186L, 
    59242536L, 89158170L, 79925652L, 90532447L, 81523935L, 118115358L, 
    123552556L, 87012356L, 66265976L, 112710053L, 114882014L), 
    percentage = c(30.6236955883, 26.8866816109, 40.4183031852, 
    41.7493687378, 41.8068248626, 40.5463120438, 55.6409038531, 
    54.7201927527, 40.9656544833, 39.5744515254, 48.5457722338, 
    47.238670909)), .Names = c("Sample", "observation1", "observation2", 
"observation3", "percentage"), class = "data.frame", row.names = c(NA, 
-12L))

# install.packages("reshape2", dependencies = TRUE)
require(reshape2)

    data1.long <- melt(df, id=c("Sample"), measure.var = c("observation1", "observation2", "observation3"))


data1.long$percentage <- paste(round(data1.long$percentage, 2), "%", sep="")
data1.long[data1.long$variable == "observation1" | data1.long$variable == "observation2" ,2] <- ""

ggplot(data1.long, aes(x = Sample, y = value, fill=variable)) + 
       geom_bar(, stat="identity", width=0.5, position="dodge") + 
       geom_text(aes(label = percentage), vjust=2.10, size=2, hjust=-.06, angle = 90)

Answer 2

您应该从Logcat发布错误，以便我们进一步帮助您。但是，根据您的显示，我发现您的代码本身没有任何错误。确保正确设置上下文。此外，如果您已参加活动，则不需要说

context.startActivity(new Intent(context,asabani_cat.class));

你可以简单地说

startActivity(new Intent(this, asabani_cat.class));

如果您不在活动中，则需要传递上下文

MyAdapter myAdapter = new MyAdapter(this);

然后在你的适配器中设置你的上下文：

MyAdapter(Context context) {
    this.context = context;
}

修改

您的logcat显示空指针异常是导致崩溃的原因。你能否在第266行发布adapter_common.java的代码？感谢

Answer 3

在科特林，您认为：

class YourClass: ArrayAdapter<Feature>(), View.OnClickListener{

   override fun getView(position: Int, convertView: View?, parent: ViewGroup): View {

       var yourView = inflater.inflate(mResource, parent, false)
       yourView .setOnClickListener(){
           onClick(convertView)
    }
  }

 override fun onClick(v: View?) {
    val intent = Intent(mContext, SeckondActivity::class.java)
    mContext.startActivity(intent)
}

}

如何在我的适配器中启动Activity？

3 个答案: